{"id":3295,"date":"2016-12-12T23:55:36","date_gmt":"2016-12-12T23:55:36","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology1\/?post_type=chapter&#038;p=3295"},"modified":"2024-04-29T16:31:26","modified_gmt":"2024-04-29T16:31:26","slug":"reading-post-translational-control-of-gene-expression","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology1\/chapter\/reading-post-translational-control-of-gene-expression\/","title":{"raw":"Post-Transcriptional Control of Gene Expression","rendered":"Post-Transcriptional Control of Gene Expression"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Understand RNA splicing and explain its role in regulating gene expression<\/li>\r\n \t<li>Describe the importance of RNA stability in gene regulation<\/li>\r\n<\/ul>\r\n<\/div>\r\nRNA is transcribed, but must be processed into a mature form before translation can begin. This processing after an RNA molecule has been transcribed, but before it is translated into a protein, is called post-transcriptional modification. As with the epigenetic and transcriptional stages of processing, this post-transcriptional step can also be regulated to control gene expression in the cell. If the RNA is not processed, shuttled, or translated, then no protein will be synthesized.\r\n<h2>RNA splicing, the first stage of post-transcriptional regulation<\/h2>\r\n<p id=\"fs-id1899262\">In eukaryotic cells, the RNA transcript often contains regions, called introns, that are removed prior to translation. The regions of RNA that code for protein are called\u00a0<strong><span id=\"term607\" data-type=\"term\">exons<\/span><\/strong>\u00a0(Figure 1). After an RNA molecule has been transcribed, but prior to its departure from the nucleus to be translated, the RNA is processed and the introns are removed by splicing. Splicing is done by spliceosomes, ribonucleoprotein complexes that can recognize the two ends of the intron, cut the transcript at those two points, and bring the exons together for ligation.<\/p>\r\n\r\n\r\n[caption id=\"attachment_3904\" align=\"aligncenter\" width=\"544\"]<img class=\"size-full wp-image-3904\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12234813\/Figure_16_05_03.jpg\" alt=\"A pre-mRNA has four exons separated by three introns. The pre-mRNA can be alternatively spliced to create two different proteins, each with three exons. One protein contains exons one, two, and three. The other protein contains exons one, three and four.\" width=\"544\" height=\"155\" \/> Figure 1. Pre-mRNA can be alternatively spliced to create different proteins.[\/caption]\r\n\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Alternative RNA Splicing<\/h3>\r\n[caption id=\"attachment_3905\" align=\"alignright\" width=\"450\"]<img class=\" wp-image-3905\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12234933\/Figure_15_04_02.jpg\" alt=\"Diagram shows five methods of alternative splicing of pre-mRNA. When exon skipping occurs, an exon is spliced out in one mature mRNA product and retained in another. When mutually exclusive exons are present in the pre-mRNA, only one is retained in the mature mRNA. When an alternative 5\u2032 donor site is present, the location of the 5\u2032 splice site is variable. When an alternative 3\u2032 acceptor site is present, the location of the 3\u2032 splice site is variable. Intron retention results in an intron being retained in one mature mRNA and spliced out in another.\" width=\"450\" height=\"427\" \/> Figure 2. There are five basic modes of alternative splicing.[\/caption]\r\n\r\nIn the 1970s, genes were first observed that exhibited alternative RNA splicing. Alternative RNA splicing is a mechanism that allows different protein products to be produced from one gene when different combinations of introns, and sometimes exons, are removed from the transcript (Figure 2). This alternative splicing can be haphazard, but more often it is controlled and acts as a mechanism of gene regulation, with the frequency of different splicing alternatives controlled by the cell as a way to control the production of different protein products in different cells or at different stages of development. Alternative splicing is now understood to be a common mechanism of gene regulation in eukaryotes; according to one estimate, 70 percent of genes in humans are expressed as multiple proteins through alternative splicing.\r\n\r\nHow could alternative splicing evolve? Introns have a beginning and ending recognition sequence; it is easy to imagine the failure of the splicing mechanism to identify the end of an intron and instead find the end of the next intron, thus removing two introns and the intervening exon. In fact, there are mechanisms in place to prevent such intron skipping, but mutations are likely to lead to their failure. Such \u201cmistakes\u201d would more than likely produce a nonfunctional protein. Indeed, the cause of many genetic diseases is alternative splicing rather than mutations in a sequence. However, alternative splicing would create a protein variant without the loss of the original protein, opening up possibilities for adaptation of the new variant to new functions. Gene duplication has played an important role in the evolution of new functions in a similar way by providing genes that may evolve without eliminating the original, functional protein.\r\n\r\n<\/div>\r\n<div>\r\n<div class=\"textbox exercises\">\r\n<h3>PRACTICE QUESTION<\/h3>\r\nIn the corn snake\u00a0<em data-effect=\"italics\">Pantherophis guttatus<\/em>, there are several different color variants, including amelanistic snakes whose skin patterns display only red and yellow pigments. The cause of amelanism in these snakes was recently identified as the insertion of a transposable element into an intron in the OCA2 (oculocutaneous albinism) gene. How might the insertion of extra genetic material into an intron lead to a nonfunctional protein?\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\">\r\n\r\nVisualize how mRNA splicing happens by watching the process in action in this video:\r\n\r\nhttps:\/\/youtu.be\/FVuAwBGw_pQ\r\n\r\n<\/div>\r\n<h2>Control of RNA Stability<\/h2>\r\n<p id=\"fs-id1703747\">Before the mRNA leaves the nucleus, it is given two protective \"caps\" that prevent the ends of the strand from degrading during its journey. 5' and 3' exonucleases can degrade unprotected RNAs. The\u00a0<strong><span id=\"term608\" data-type=\"term\">5' cap<\/span><\/strong>, which is placed on the 5' end of the mRNA, is usually composed of a methylated guanosine triphosphate molecule (GTP). The GTP is placed \"backward\" on the 5' end of the mRNA, so that the 5' carbons of the GTP and the terminal nucleotide are linked through three phosphates. The\u00a0<strong><span id=\"term609\" data-type=\"term\">poly-A tail<\/span><\/strong>, which is attached to the 3' end, is usually composed of a long chain of adenine nucleotides. These changes protect the two ends of the RNA from exonuclease attack.<\/p>\r\n<p id=\"fs-id1714747\">Once the RNA is transported to the cytoplasm, the length of time that the RNA resides there can be controlled. Each RNA molecule has a defined lifespan and decays at a specific rate. This rate of decay can influence how much protein is in the cell. If the decay rate is increased, the RNA will not exist in the cytoplasm as long, shortening the time available for translation of the mRNA to occur. Conversely, if the rate of decay is decreased, the mRNA molecule will reside in the cytoplasm longer and more protein can be translated. This rate of decay is referred to as the RNA stability. If the RNA is stable, it will be detected for longer periods of time in the cytoplasm.<\/p>\r\n<p id=\"fs-id2167834\">Binding of proteins to the RNA can also influence its stability. Proteins called\u00a0<strong><span id=\"term610\" data-type=\"term\">RNA-binding proteins<\/span><\/strong>, or RBPs, can bind to the regions of the mRNA just upstream or downstream of the protein-coding region. These regions in the RNA that are not translated into protein are called the\u00a0<strong><span id=\"term611\" data-type=\"term\">untranslated regions<\/span><\/strong>, or UTRs. They are not introns (those have been removed in the nucleus). Rather, these are regions that regulate mRNA localization, stability, and protein translation. The region just before the protein-coding region is called the\u00a0<strong><span id=\"term612\" data-type=\"term\">5' UTR<\/span><\/strong>, whereas the region after the coding region is called the\u00a0<strong><span id=\"term613\" data-type=\"term\">3' UTR<\/span><\/strong>\u00a0(Figure 3). The binding of RBPs to these regions can increase or decrease the stability of an RNA molecule, depending on the specific RBP that binds.<\/p>\r\n\r\n\r\n[caption id=\"attachment_3906\" align=\"aligncenter\" width=\"800\"]<img class=\"size-full wp-image-3906\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12235214\/Figure_16_05_02.jpg\" alt=\"In the mature RNA molecule, exons are spliced together between the 5\u2032 and 3\u2032 untranslated regions. A 5\u2032 cap is attached to the 5\u2032 untranslated region, and a poly-A tail is attached to the 3\u2032 untranslated region. RNA-binding proteins associate with the 5\u2032 and 3\u2032 untranslated regions.\" width=\"800\" height=\"170\" \/> Figure 3. The protein-coding region of mRNA is flanked by 5\u2032 and 3\u2032 untranslated regions (UTRs). The presence of RNA-binding proteins at the 5\u2032 or 3\u2032 UTR influences the stability of the RNA molecule.[\/caption]\r\n<h2>RNA Stability and microRNAs<\/h2>\r\nIn addition to RBPs that bind to and control (increase or decrease) RNA stability, other elements called microRNAs can bind to the RNA molecule. These <strong>microRNAs<\/strong>, or miRNAs, are short RNA molecules that are only 21\u201324 nucleotides in length. The miRNAs are made in the nucleus as longer pre-miRNAs. These pre-miRNAs are chopped into mature miRNAs by a protein called <strong>dicer<\/strong>. Like transcription factors and RBPs, mature miRNAs recognize a specific sequence and bind to the RNA; however, miRNAs also associate with a ribonucleoprotein complex called the <strong>RNA-induced silencing complex (RISC)<\/strong>. RISC binds along with the miRNA to degrade the target mRNA. Together, miRNAs and the RISC complex rapidly destroy the RNA molecule.\r\n<div class=\"textbox learning-objectives\">\r\n<h3>In Summary: Post-TransCRIPTIONAL Control of Gene Expression<\/h3>\r\nPost-transcriptional control can occur at any stage after transcription, including RNA splicing, nuclear shuttling, and RNA stability. Once RNA is transcribed, it must be processed to create a mature RNA that is ready to be translated. This involves the removal of introns that do not code for protein. Spliceosomes bind to the signals that mark the exon\/intron border to remove the introns and ligate the exons together. Once this occurs, the RNA is mature and can be translated. RNA is created and spliced in the nucleus, but needs to be transported to the cytoplasm to be translated. RNA is transported to the cytoplasm through the nuclear pore complex. Once the RNA is in the cytoplasm, the length of time it resides there before being degraded, called RNA stability, can also be altered to control the overall amount of protein that is synthesized. The RNA stability can be increased, leading to longer residency time in the cytoplasm, or decreased, leading to shortened time and less protein synthesis. RNA stability is controlled by RNA-binding proteins (RPBs) and microRNAs (miRNAs). These RPBs and miRNAs bind to the 5\u2032 UTR or the 3\u2032 UTR of the RNA to increase or decrease RNA stability. Depending on the RBP, the stability can be increased or decreased significantly; however, miRNAs always decrease stability and promote decay.\r\n\r\n<\/div>\r\n<div class=\"textbox exercises\">\r\n<h3>Practice Questions<\/h3>\r\nWhich of the following are involved in post-transcriptional control?\r\n<ol style=\"list-style-type: lower-alpha;\">\r\n \t<li>control of RNA splicing<\/li>\r\n \t<li>control of RNA shuttling<\/li>\r\n \t<li>control of RNA stability<\/li>\r\n \t<li>all of the above<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"681081\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"681081\"]Answer d. All of the above (control of RNA splicing, RNA shuttling, and RNA stability)\u00a0are involved in post-transcriptional control.\r\n\r\n[\/hidden-answer]\r\n\r\nBinding of an RNA binding protein will ________ the stability of the RNA molecule.\r\n<ol style=\"list-style-type: lower-alpha;\">\r\n \t<li>increase<\/li>\r\n \t<li>decrease<\/li>\r\n \t<li>neither increase nor decrease<\/li>\r\n \t<li>either increase or decrease<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"464261\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"464261\"]Answer d. Binding of an RNA binding protein will either increase or decrease the stability of the RNA molecule.\r\n\r\n[\/hidden-answer]\r\n\r\nDescribe how RBPs can prevent miRNAs from degrading an RNA molecule.\r\n\r\n[practice-area rows=\"2\"][\/practice-area]\r\n[reveal-answer q=\"16680\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"16680\"]RNA binding proteins (RBP) bind to the RNA and can either increase or decrease the stability of the RNA. If they increase the stability of the RNA molecule, the RNA will remain intact in the cell for a longer period of time than normal. Since both RBPs and miRNAs bind to the RNA molecule, RBP can potentially bind first to the RNA and prevent the binding of the miRNA that will degrade it.\r\n\r\n[\/hidden-answer]\r\n\r\nHow can external stimuli alter post-transcriptional control of gene expression?\r\n\r\n[practice-area rows=\"2\"][\/practice-area]\r\n[reveal-answer q=\"598728\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"598728\"]External stimuli can modify RNA-binding proteins (i.e., through phosphorylation of proteins) to alter their activity.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/249f19af-f5fb-418f-856b-d05f6c3646c9\r\nhttps:\/\/assess.lumenlearning.com\/practice\/838c8ec6-870a-4e23-a4fe-fd8f422c3585\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Understand RNA splicing and explain its role in regulating gene expression<\/li>\n<li>Describe the importance of RNA stability in gene regulation<\/li>\n<\/ul>\n<\/div>\n<p>RNA is transcribed, but must be processed into a mature form before translation can begin. This processing after an RNA molecule has been transcribed, but before it is translated into a protein, is called post-transcriptional modification. As with the epigenetic and transcriptional stages of processing, this post-transcriptional step can also be regulated to control gene expression in the cell. If the RNA is not processed, shuttled, or translated, then no protein will be synthesized.<\/p>\n<h2>RNA splicing, the first stage of post-transcriptional regulation<\/h2>\n<p id=\"fs-id1899262\">In eukaryotic cells, the RNA transcript often contains regions, called introns, that are removed prior to translation. The regions of RNA that code for protein are called\u00a0<strong><span id=\"term607\" data-type=\"term\">exons<\/span><\/strong>\u00a0(Figure 1). After an RNA molecule has been transcribed, but prior to its departure from the nucleus to be translated, the RNA is processed and the introns are removed by splicing. Splicing is done by spliceosomes, ribonucleoprotein complexes that can recognize the two ends of the intron, cut the transcript at those two points, and bring the exons together for ligation.<\/p>\n<div id=\"attachment_3904\" style=\"width: 554px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3904\" class=\"size-full wp-image-3904\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12234813\/Figure_16_05_03.jpg\" alt=\"A pre-mRNA has four exons separated by three introns. The pre-mRNA can be alternatively spliced to create two different proteins, each with three exons. One protein contains exons one, two, and three. The other protein contains exons one, three and four.\" width=\"544\" height=\"155\" \/><\/p>\n<p id=\"caption-attachment-3904\" class=\"wp-caption-text\">Figure 1. Pre-mRNA can be alternatively spliced to create different proteins.<\/p>\n<\/div>\n<div class=\"textbox key-takeaways\">\n<h3>Alternative RNA Splicing<\/h3>\n<div id=\"attachment_3905\" style=\"width: 460px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3905\" class=\"wp-image-3905\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12234933\/Figure_15_04_02.jpg\" alt=\"Diagram shows five methods of alternative splicing of pre-mRNA. When exon skipping occurs, an exon is spliced out in one mature mRNA product and retained in another. When mutually exclusive exons are present in the pre-mRNA, only one is retained in the mature mRNA. When an alternative 5\u2032 donor site is present, the location of the 5\u2032 splice site is variable. When an alternative 3\u2032 acceptor site is present, the location of the 3\u2032 splice site is variable. Intron retention results in an intron being retained in one mature mRNA and spliced out in another.\" width=\"450\" height=\"427\" \/><\/p>\n<p id=\"caption-attachment-3905\" class=\"wp-caption-text\">Figure 2. There are five basic modes of alternative splicing.<\/p>\n<\/div>\n<p>In the 1970s, genes were first observed that exhibited alternative RNA splicing. Alternative RNA splicing is a mechanism that allows different protein products to be produced from one gene when different combinations of introns, and sometimes exons, are removed from the transcript (Figure 2). This alternative splicing can be haphazard, but more often it is controlled and acts as a mechanism of gene regulation, with the frequency of different splicing alternatives controlled by the cell as a way to control the production of different protein products in different cells or at different stages of development. Alternative splicing is now understood to be a common mechanism of gene regulation in eukaryotes; according to one estimate, 70 percent of genes in humans are expressed as multiple proteins through alternative splicing.<\/p>\n<p>How could alternative splicing evolve? Introns have a beginning and ending recognition sequence; it is easy to imagine the failure of the splicing mechanism to identify the end of an intron and instead find the end of the next intron, thus removing two introns and the intervening exon. In fact, there are mechanisms in place to prevent such intron skipping, but mutations are likely to lead to their failure. Such \u201cmistakes\u201d would more than likely produce a nonfunctional protein. Indeed, the cause of many genetic diseases is alternative splicing rather than mutations in a sequence. However, alternative splicing would create a protein variant without the loss of the original protein, opening up possibilities for adaptation of the new variant to new functions. Gene duplication has played an important role in the evolution of new functions in a similar way by providing genes that may evolve without eliminating the original, functional protein.<\/p>\n<\/div>\n<div>\n<div class=\"textbox exercises\">\n<h3>PRACTICE QUESTION<\/h3>\n<p>In the corn snake\u00a0<em data-effect=\"italics\">Pantherophis guttatus<\/em>, there are several different color variants, including amelanistic snakes whose skin patterns display only red and yellow pigments. The cause of amelanism in these snakes was recently identified as the insertion of a transposable element into an intron in the OCA2 (oculocutaneous albinism) gene. How might the insertion of extra genetic material into an intron lead to a nonfunctional protein?<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\">\n<p>Visualize how mRNA splicing happens by watching the process in action in this video:<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"mRNA Splicing\" width=\"500\" height=\"375\" src=\"https:\/\/www.youtube.com\/embed\/FVuAwBGw_pQ?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<\/div>\n<h2>Control of RNA Stability<\/h2>\n<p id=\"fs-id1703747\">Before the mRNA leaves the nucleus, it is given two protective &#8220;caps&#8221; that prevent the ends of the strand from degrading during its journey. 5&#8242; and 3&#8242; exonucleases can degrade unprotected RNAs. The\u00a0<strong><span id=\"term608\" data-type=\"term\">5&#8242; cap<\/span><\/strong>, which is placed on the 5&#8242; end of the mRNA, is usually composed of a methylated guanosine triphosphate molecule (GTP). The GTP is placed &#8220;backward&#8221; on the 5&#8242; end of the mRNA, so that the 5&#8242; carbons of the GTP and the terminal nucleotide are linked through three phosphates. The\u00a0<strong><span id=\"term609\" data-type=\"term\">poly-A tail<\/span><\/strong>, which is attached to the 3&#8242; end, is usually composed of a long chain of adenine nucleotides. These changes protect the two ends of the RNA from exonuclease attack.<\/p>\n<p id=\"fs-id1714747\">Once the RNA is transported to the cytoplasm, the length of time that the RNA resides there can be controlled. Each RNA molecule has a defined lifespan and decays at a specific rate. This rate of decay can influence how much protein is in the cell. If the decay rate is increased, the RNA will not exist in the cytoplasm as long, shortening the time available for translation of the mRNA to occur. Conversely, if the rate of decay is decreased, the mRNA molecule will reside in the cytoplasm longer and more protein can be translated. This rate of decay is referred to as the RNA stability. If the RNA is stable, it will be detected for longer periods of time in the cytoplasm.<\/p>\n<p id=\"fs-id2167834\">Binding of proteins to the RNA can also influence its stability. Proteins called\u00a0<strong><span id=\"term610\" data-type=\"term\">RNA-binding proteins<\/span><\/strong>, or RBPs, can bind to the regions of the mRNA just upstream or downstream of the protein-coding region. These regions in the RNA that are not translated into protein are called the\u00a0<strong><span id=\"term611\" data-type=\"term\">untranslated regions<\/span><\/strong>, or UTRs. They are not introns (those have been removed in the nucleus). Rather, these are regions that regulate mRNA localization, stability, and protein translation. The region just before the protein-coding region is called the\u00a0<strong><span id=\"term612\" data-type=\"term\">5&#8242; UTR<\/span><\/strong>, whereas the region after the coding region is called the\u00a0<strong><span id=\"term613\" data-type=\"term\">3&#8242; UTR<\/span><\/strong>\u00a0(Figure 3). The binding of RBPs to these regions can increase or decrease the stability of an RNA molecule, depending on the specific RBP that binds.<\/p>\n<div id=\"attachment_3906\" style=\"width: 810px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3906\" class=\"size-full wp-image-3906\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2016\/12\/12235214\/Figure_16_05_02.jpg\" alt=\"In the mature RNA molecule, exons are spliced together between the 5\u2032 and 3\u2032 untranslated regions. A 5\u2032 cap is attached to the 5\u2032 untranslated region, and a poly-A tail is attached to the 3\u2032 untranslated region. RNA-binding proteins associate with the 5\u2032 and 3\u2032 untranslated regions.\" width=\"800\" height=\"170\" \/><\/p>\n<p id=\"caption-attachment-3906\" class=\"wp-caption-text\">Figure 3. The protein-coding region of mRNA is flanked by 5\u2032 and 3\u2032 untranslated regions (UTRs). The presence of RNA-binding proteins at the 5\u2032 or 3\u2032 UTR influences the stability of the RNA molecule.<\/p>\n<\/div>\n<h2>RNA Stability and microRNAs<\/h2>\n<p>In addition to RBPs that bind to and control (increase or decrease) RNA stability, other elements called microRNAs can bind to the RNA molecule. These <strong>microRNAs<\/strong>, or miRNAs, are short RNA molecules that are only 21\u201324 nucleotides in length. The miRNAs are made in the nucleus as longer pre-miRNAs. These pre-miRNAs are chopped into mature miRNAs by a protein called <strong>dicer<\/strong>. Like transcription factors and RBPs, mature miRNAs recognize a specific sequence and bind to the RNA; however, miRNAs also associate with a ribonucleoprotein complex called the <strong>RNA-induced silencing complex (RISC)<\/strong>. RISC binds along with the miRNA to degrade the target mRNA. Together, miRNAs and the RISC complex rapidly destroy the RNA molecule.<\/p>\n<div class=\"textbox learning-objectives\">\n<h3>In Summary: Post-TransCRIPTIONAL Control of Gene Expression<\/h3>\n<p>Post-transcriptional control can occur at any stage after transcription, including RNA splicing, nuclear shuttling, and RNA stability. Once RNA is transcribed, it must be processed to create a mature RNA that is ready to be translated. This involves the removal of introns that do not code for protein. Spliceosomes bind to the signals that mark the exon\/intron border to remove the introns and ligate the exons together. Once this occurs, the RNA is mature and can be translated. RNA is created and spliced in the nucleus, but needs to be transported to the cytoplasm to be translated. RNA is transported to the cytoplasm through the nuclear pore complex. Once the RNA is in the cytoplasm, the length of time it resides there before being degraded, called RNA stability, can also be altered to control the overall amount of protein that is synthesized. The RNA stability can be increased, leading to longer residency time in the cytoplasm, or decreased, leading to shortened time and less protein synthesis. RNA stability is controlled by RNA-binding proteins (RPBs) and microRNAs (miRNAs). These RPBs and miRNAs bind to the 5\u2032 UTR or the 3\u2032 UTR of the RNA to increase or decrease RNA stability. Depending on the RBP, the stability can be increased or decreased significantly; however, miRNAs always decrease stability and promote decay.<\/p>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Practice Questions<\/h3>\n<p>Which of the following are involved in post-transcriptional control?<\/p>\n<ol style=\"list-style-type: lower-alpha;\">\n<li>control of RNA splicing<\/li>\n<li>control of RNA shuttling<\/li>\n<li>control of RNA stability<\/li>\n<li>all of the above<\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q681081\">Show Answer<\/span><\/p>\n<div id=\"q681081\" class=\"hidden-answer\" style=\"display: none\">Answer d. All of the above (control of RNA splicing, RNA shuttling, and RNA stability)\u00a0are involved in post-transcriptional control.<\/p>\n<\/div>\n<\/div>\n<p>Binding of an RNA binding protein will ________ the stability of the RNA molecule.<\/p>\n<ol style=\"list-style-type: lower-alpha;\">\n<li>increase<\/li>\n<li>decrease<\/li>\n<li>neither increase nor decrease<\/li>\n<li>either increase or decrease<\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q464261\">Show Answer<\/span><\/p>\n<div id=\"q464261\" class=\"hidden-answer\" style=\"display: none\">Answer d. Binding of an RNA binding protein will either increase or decrease the stability of the RNA molecule.<\/p>\n<\/div>\n<\/div>\n<p>Describe how RBPs can prevent miRNAs from degrading an RNA molecule.<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q16680\">Show Answer<\/span><\/p>\n<div id=\"q16680\" class=\"hidden-answer\" style=\"display: none\">RNA binding proteins (RBP) bind to the RNA and can either increase or decrease the stability of the RNA. If they increase the stability of the RNA molecule, the RNA will remain intact in the cell for a longer period of time than normal. Since both RBPs and miRNAs bind to the RNA molecule, RBP can potentially bind first to the RNA and prevent the binding of the miRNA that will degrade it.<\/p>\n<\/div>\n<\/div>\n<p>How can external stimuli alter post-transcriptional control of gene expression?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q598728\">Show Answer<\/span><\/p>\n<div id=\"q598728\" class=\"hidden-answer\" style=\"display: none\">External stimuli can modify RNA-binding proteins (i.e., through phosphorylation of proteins) to alter their activity.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_249f19af-f5fb-418f-856b-d05f6c3646c9\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/249f19af-f5fb-418f-856b-d05f6c3646c9?iframe_resize_id=assessment_practice_id_249f19af-f5fb-418f-856b-d05f6c3646c9\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe><br \/>\n\t<iframe id=\"assessment_practice_838c8ec6-870a-4e23-a4fe-fd8f422c3585\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/838c8ec6-870a-4e23-a4fe-fd8f422c3585?iframe_resize_id=assessment_practice_id_838c8ec6-870a-4e23-a4fe-fd8f422c3585\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-3295\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":13,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"17c2da93-8ad9-4bf9-8290-3e9a7b6ac403, 5c639282-a339-47f9-b8f5-8f8f4a4ec0cd, 8f9703ef-d925-42f5-a232-82f0a6eeb7d1","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-3295","chapter","type-chapter","status-publish","hentry"],"part":3270,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/3295","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":16,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/3295\/revisions"}],"predecessor-version":[{"id":6002,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/3295\/revisions\/6002"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/parts\/3270"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/3295\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/media?parent=3295"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapter-type?post=3295"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/contributor?post=3295"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/license?post=3295"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}