{"id":238,"date":"2023-03-11T15:50:27","date_gmt":"2023-03-11T15:50:27","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/?post_type=chapter&#038;p=238"},"modified":"2023-04-07T09:55:24","modified_gmt":"2023-04-07T09:55:24","slug":"prokaryotic-transcription","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/chapter\/prokaryotic-transcription\/","title":{"raw":"Prokaryotic Transcription- Initiation","rendered":"Prokaryotic Transcription- Initiation"},"content":{"raw":"<p style=\"text-align: justify\"><span><strong><em>The process of\u00a0<\/em> transcription occurs in the nucleus of the cell in eukaryotes<\/strong>\u00a0 and the mRNA transcript must be transported to the cytoplasm for protein synthesis . <em><strong>In prokaryotes, which lack membrane-bound nuclei and other organelles, transcription occurs in the cytoplasm of the cell. <\/strong><\/em>Therefore, the processes of transcription and\u00a0 translation,\u00a0 can all occur simultaneously. This is referred to as\u00a0 <strong>[pb_glossary id=\"923\"]Coupled Transcription- Translation [\/pb_glossary].<\/strong> The intracellular level of a bacterial protein can quickly be amplified by multiple transcription and translation events occurring concurrently on the same DNA template. Prokaryotic transcription often covers more than one gene and produces polycistronic mRNAs that specify more than one protein.<\/span><\/p>\r\n\r\n<h1 style=\"text-align: justify\">Prokaryotic RNA Polymerase<\/h1>\r\n<ul style=\"text-align: justify\">\r\n \t<li><span>The process of transcription begins when an\u00a0<\/span><span class=\"ontologyTermLink\">enzyme<\/span><span>\u00a0called RNA Polymerase\u00a0 which <\/span><span>attaches to the template DNA strand and begins to catalyze production of\u00a0<\/span><span class=\"glossaryTermLink\">complementary<\/span><span>\u00a0RNA. <\/span>Prokaryotes use the same RNA polymerase to transcribe all of their genes.<\/li>\r\n \t<li>In<span>\u00a0<\/span><em>E. coli<\/em>, the polymerase is composed of five polypeptide subunits, comprising the <strong>Core enzyme<\/strong>\u00a0 and the <strong>holoenzyme .<\/strong><\/li>\r\n \t<li>The five subunits include\r\n<ul>\r\n \t<li><strong>\u00a0two\u00a0<em>\u03b1<\/em>-subunits\u00a0<\/strong> :\u00a0 are necessary to assemble the polymerase on the DNA<\/li>\r\n \t<li><strong>\u00a0<em>\u03b2<\/em>-subunit :<\/strong>\u00a0 binds to the ribonucleoside triphosphate that will become part of the nascent \u201crecently born\u201d mRNA molecule;<\/li>\r\n \t<li><strong>\u00a0<em>\u03b2<\/em>\u2032 - subunit\u00a0 :<\/strong> binds the DNA template strand.<\/li>\r\n \t<li><strong>\u00a0subunit\u00a0 <\/strong><em><strong>\u03c3\u00a0<\/strong> : <\/em>is involved only in transcription initiation. It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site. Without<span>\u00a0<\/span><em>\u03c3<\/em>, the core enzyme would transcribe from random sites<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\"><span>The\u00a0 <\/span><em>\u03b1<\/em>,<span>\u00a0<\/span><em>\u03b1<\/em>,<span>\u00a0<\/span><em>\u03b2<\/em>, and<span>\u00a0<\/span><em>\u03b2<\/em>\u2032 comprise the polymerase<span>\u00a0<\/span><strong>core enzyme<\/strong>. The polymerase comprised of all five subunits is called the<span>\u00a0<\/span><strong>[pb_glossary id=\"929\"]holoenzyme[\/pb_glossary]<span>\u00a0<\/span><\/strong>(a holoenzyme is a biochemically active and is comprised of an enzyme and its coenzyme).<\/p>\r\n\r\n<h1 style=\"text-align: center\">The Process of Prokaryotic Transcription<\/h1>\r\n<p style=\"text-align: justify\"><strong>Template or Non coding strand\u00a0<\/strong><\/p>\r\n<p style=\"text-align: justify\"><span>DNA is double-stranded, but only one strand serves as a template for transcription at any given time. This<\/span>[pb_glossary id=\"925\"]<span><strong>\u00a0<\/strong><\/span><strong><span class=\"glossaryTermLink\">template strand<\/span><\/strong>[\/pb_glossary]<span class=\"glossaryTermLink\"><\/span><span><strong>\u00a0<\/strong>is called the <strong>noncoding strand. <\/strong><\/span><\/p>\r\n<p style=\"text-align: justify\"><strong>Non template or Coding strand\u00a0<\/strong><\/p>\r\n<p style=\"text-align: justify\"><span>The other strand of DNA which is not serving as template is called the\u00a0 <\/span><span class=\"glossaryTermLink\"><strong>[pb_glossary id=\"927\"]nontemplate[\/pb_glossary]\u00a0 or coding strand .<\/strong> This strand<\/span><span>\u00a0is referred to as the coding strand because its sequence will be the same as that of the new RNA molecule. In most organisms, the strand of DNA that serves as the template for one\u00a0<\/span><span class=\"ontologyTermLink\">gene<\/span><span>\u00a0may be the nontemplate strand for other\u00a0<\/span><span class=\"glossaryTermLink\">genes<\/span><span>\u00a0within the same\u00a0<\/span><span class=\"ontologyTermLink\">chromosome<\/span><span>.<\/span><\/p>\r\n<p style=\"text-align: justify\"><strong>Upstream and Down stream Sequences\u00a0<\/strong><\/p>\r\n<p style=\"text-align: justify\"><span>These are\u00a0 conventions used to describe features of a DNA sequence, gene or mRNA related to the position and direction (5' to 3') of transcription by RNA polymerase or translation by the ribosome. <\/span><\/p>\r\n<p style=\"text-align: justify\"><span><strong>Downstream (or 3' to) is in the direction of transcription (or translation<\/strong>) whereas<\/span><\/p>\r\n<p style=\"text-align: justify\"><span>Upstream (5' to) is in the direction from which the polymerase (or ribosome) has come.( Upstream DNA sequences are before the start site of transcription)<\/span><\/p>\r\n<img src=\"http:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-1024x576.jpg\" alt=\"Picture depicting the template and non tempalte stand, transcription bubble\" width=\"676\" height=\"380\" class=\"aligncenter wp-image-270\" \/>\r\n<p style=\"text-align: center\"><span style=\"background-color: #ffffff\">Image<span style=\"color: #993366\"><a href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Transcription_bubble.jpg\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\"> \"Transcription Bubble\"<\/a>\u00a0by\u00a0<a style=\"color: #993366;background-color: #ffffff\">Ristinn via Wikimedia Commons<\/a>\u00a0is licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by-sa\/4.0\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\">CC BY-SA 4.0<\/a><\/span><\/span><\/p>\r\n\r\n<h1 style=\"text-align: justify\">INITIATION<\/h1>\r\n<p style=\"text-align: justify\"><span>The first step in transcription is initiation, when the RNA pol binds to the DNA\u00a0<\/span><span class=\"glossaryTermLink\">upstream<\/span><span>\u00a0(5\u2032) of the gene at a specialized sequence called a\u00a0<\/span><span class=\"ontologyTermLink\">promoter<\/span><span> .<\/span><\/p>\r\n\r\n<h2 style=\"text-align: justify\">Prokaryotic Promoters<\/h2>\r\n<ul style=\"text-align: justify\">\r\n \t<li><span>The DNA sequence onto which the proteins and enzymes involved in transcription bind to initiate the process is called a<\/span>[pb_glossary id=\"932\"]<span>\u00a0<\/span><strong>promoter<\/strong>[\/pb_glossary]<span>. Promoters usually exist upstream of the genes they regulate. The specific sequence of a promoter determines whether the corresponding gene is transcribed all of the time, some of the time, or hardly at all. The structure and function of a prokaryotic promoter is relatively simple\u00a0<\/span><\/li>\r\n \t<li><span style=\"font-size: 1em\"><strong>The -10 consensus sequence or the Pribnow box\u00a0<\/strong> : In prokaryotes, most genes have a sequence called the Pribnow box, with the <\/span><span class=\"ontologyTermLink\" style=\"font-size: 1em\">consensus sequence<\/span><span style=\"font-size: 1em\"><strong> TATAAT<\/strong> positioned about ten base pairs away from the site . This serves as the location of transcription initiation. Not all Pribnow boxes have this exact nucleotide sequence; these nucleotides are simply the most common ones found at each site.<\/span><\/li>\r\n \t<li><strong>The -35 consensus sequence :<\/strong> <span style=\"font-size: 1em\">Many genes also have the consensus sequence<\/span><strong><span style=\"font-size: 1em\"> TTGCCA <\/span><\/strong><span style=\"font-size: 1em\">at -35\u00a0 position, up<\/span><span style=\"text-align: initial;font-size: 1em\">stream of the start site<\/span><\/li>\r\n \t<li><strong><span class=\"glossaryTermLink\" style=\"text-align: initial;font-size: 1em\">Upstream element\u00a0 : <\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">an A-T rich region 40 to 60 nucleotides upstream that enhances the rate of transcription<\/span><\/li>\r\n<\/ul>\r\n<img src=\"http:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter.jpg\" alt=\" Figure depicting the promoter elements in prokaryotes \" width=\"544\" height=\"243\" class=\"aligncenter size-full wp-image-268\" \/>\r\n<p style=\"text-align: center\"><span id=\"output\" class=\"outputbox\"><span style=\"color: #993366;background-color: #ffffff\">\"Prokaryotic Promoter\" Image from <a href=\"https:\/\/openstax.org\/books\/biology-2e\/pages\/15-2-prokaryotic-transcription\" style=\"background-color: #ffffff\"><em data-effect=\"italics\">Biology 2e<\/em>\u00a0(2nd edition), an OpenStax resource<\/a>\u00a0licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by\/4.0\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\">CC BY 4.0<\/a><\/span><a><\/a><\/span><span><\/span><\/p>\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">\u00a0The process of transcription starts with the binding of\u00a0 the RNA pol \"holo<\/span><span class=\"glossaryTermLink\" style=\"text-align: initial;font-size: 1em\">enzyme<\/span><span style=\"text-align: initial;font-size: 1em\">\" binding to the template DNA and\u00a0 unwinds\u00a0 the DNA <\/span><span class=\"ontologyTermLink\" style=\"text-align: initial;font-size: 1em\">double helix<\/span><span style=\"text-align: initial;font-size: 1em\"> in order to facilitate access to the gene. The sigma subunit conveys promoter specificity to RNA polymerase; that is, it instructs the\u00a0 RNA polymerase where to bind. There are a number of different sigma subunits that bind to different promoters. These sigma subunits assist in turning genes on and off as conditions change.<\/span><\/p>\r\n<span>The mRNA product is complementary to the template strand and is almost identical to the other DNA strand, called the\u00a0<\/span><strong>non-template strand<\/strong><span>, with the exception that RNA contains a uracil (U) in place of the thymine (T) found in DNA. Like DNA polymerase, RNA polymerase adds new nucleotides onto the 3\u2032-OH group of the previous nucleotide. This means that the growing mRNA strand is being synthesized in the 5\u2032 to 3\u2032 direction.\u00a0<\/span>","rendered":"<p style=\"text-align: justify\"><span><strong><em>The process of\u00a0<\/em> transcription occurs in the nucleus of the cell in eukaryotes<\/strong>\u00a0 and the mRNA transcript must be transported to the cytoplasm for protein synthesis . <em><strong>In prokaryotes, which lack membrane-bound nuclei and other organelles, transcription occurs in the cytoplasm of the cell. <\/strong><\/em>Therefore, the processes of transcription and\u00a0 translation,\u00a0 can all occur simultaneously. This is referred to as\u00a0 <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_238_923\">Coupled Transcription- Translation <\/a>.<\/strong> The intracellular level of a bacterial protein can quickly be amplified by multiple transcription and translation events occurring concurrently on the same DNA template. Prokaryotic transcription often covers more than one gene and produces polycistronic mRNAs that specify more than one protein.<\/span><\/p>\n<h1 style=\"text-align: justify\">Prokaryotic RNA Polymerase<\/h1>\n<ul style=\"text-align: justify\">\n<li><span>The process of transcription begins when an\u00a0<\/span><span class=\"ontologyTermLink\">enzyme<\/span><span>\u00a0called RNA Polymerase\u00a0 which <\/span><span>attaches to the template DNA strand and begins to catalyze production of\u00a0<\/span><span class=\"glossaryTermLink\">complementary<\/span><span>\u00a0RNA. <\/span>Prokaryotes use the same RNA polymerase to transcribe all of their genes.<\/li>\n<li>In<span>\u00a0<\/span><em>E. coli<\/em>, the polymerase is composed of five polypeptide subunits, comprising the <strong>Core enzyme<\/strong>\u00a0 and the <strong>holoenzyme .<\/strong><\/li>\n<li>The five subunits include\n<ul>\n<li><strong>\u00a0two\u00a0<em>\u03b1<\/em>-subunits\u00a0<\/strong> :\u00a0 are necessary to assemble the polymerase on the DNA<\/li>\n<li><strong>\u00a0<em>\u03b2<\/em>-subunit :<\/strong>\u00a0 binds to the ribonucleoside triphosphate that will become part of the nascent \u201crecently born\u201d mRNA molecule;<\/li>\n<li><strong>\u00a0<em>\u03b2<\/em>\u2032 &#8211; subunit\u00a0 :<\/strong> binds the DNA template strand.<\/li>\n<li><strong>\u00a0subunit\u00a0 <\/strong><em><strong>\u03c3\u00a0<\/strong> : <\/em>is involved only in transcription initiation. It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site. Without<span>\u00a0<\/span><em>\u03c3<\/em>, the core enzyme would transcribe from random sites<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p style=\"text-align: justify\"><span>The\u00a0 <\/span><em>\u03b1<\/em>,<span>\u00a0<\/span><em>\u03b1<\/em>,<span>\u00a0<\/span><em>\u03b2<\/em>, and<span>\u00a0<\/span><em>\u03b2<\/em>\u2032 comprise the polymerase<span>\u00a0<\/span><strong>core enzyme<\/strong>. The polymerase comprised of all five subunits is called the<span>\u00a0<\/span><strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_238_929\">holoenzyme<\/a><span>\u00a0<\/span><\/strong>(a holoenzyme is a biochemically active and is comprised of an enzyme and its coenzyme).<\/p>\n<h1 style=\"text-align: center\">The Process of Prokaryotic Transcription<\/h1>\n<p style=\"text-align: justify\"><strong>Template or Non coding strand\u00a0<\/strong><\/p>\n<p style=\"text-align: justify\"><span>DNA is double-stranded, but only one strand serves as a template for transcription at any given time. This<\/span><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_238_925\"><span><strong>\u00a0<\/strong><\/span><strong><span class=\"glossaryTermLink\">template strand<\/span><\/strong><\/a><span class=\"glossaryTermLink\"><\/span><span><strong>\u00a0<\/strong>is called the <strong>noncoding strand. <\/strong><\/span><\/p>\n<p style=\"text-align: justify\"><strong>Non template or Coding strand\u00a0<\/strong><\/p>\n<p style=\"text-align: justify\"><span>The other strand of DNA which is not serving as template is called the\u00a0 <\/span><span class=\"glossaryTermLink\"><strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_238_927\">nontemplate<\/a>\u00a0 or coding strand .<\/strong> This strand<\/span><span>\u00a0is referred to as the coding strand because its sequence will be the same as that of the new RNA molecule. In most organisms, the strand of DNA that serves as the template for one\u00a0<\/span><span class=\"ontologyTermLink\">gene<\/span><span>\u00a0may be the nontemplate strand for other\u00a0<\/span><span class=\"glossaryTermLink\">genes<\/span><span>\u00a0within the same\u00a0<\/span><span class=\"ontologyTermLink\">chromosome<\/span><span>.<\/span><\/p>\n<p style=\"text-align: justify\"><strong>Upstream and Down stream Sequences\u00a0<\/strong><\/p>\n<p style=\"text-align: justify\"><span>These are\u00a0 conventions used to describe features of a DNA sequence, gene or mRNA related to the position and direction (5&#8242; to 3&#8242;) of transcription by RNA polymerase or translation by the ribosome. <\/span><\/p>\n<p style=\"text-align: justify\"><span><strong>Downstream (or 3&#8242; to) is in the direction of transcription (or translation<\/strong>) whereas<\/span><\/p>\n<p style=\"text-align: justify\"><span>Upstream (5&#8242; to) is in the direction from which the polymerase (or ribosome) has come.( Upstream DNA sequences are before the start site of transcription)<\/span><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-1024x576.jpg\" alt=\"Picture depicting the template and non tempalte stand, transcription bubble\" width=\"676\" height=\"380\" class=\"aligncenter wp-image-270\" srcset=\"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-1024x576.jpg 1024w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-300x169.jpg 300w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-768x432.jpg 768w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-65x37.jpg 65w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-225x127.jpg 225w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble-350x197.jpg 350w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/Transcription_bubble.jpg 1200w\" sizes=\"(max-width: 676px) 100vw, 676px\" \/><\/p>\n<p style=\"text-align: center\"><span style=\"background-color: #ffffff\">Image<span style=\"color: #993366\"><a href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Transcription_bubble.jpg\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\"> &#8220;Transcription Bubble&#8221;<\/a>\u00a0by\u00a0<a style=\"color: #993366;background-color: #ffffff\">Ristinn via Wikimedia Commons<\/a>\u00a0is licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by-sa\/4.0\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\">CC BY-SA 4.0<\/a><\/span><\/span><\/p>\n<h1 style=\"text-align: justify\">INITIATION<\/h1>\n<p style=\"text-align: justify\"><span>The first step in transcription is initiation, when the RNA pol binds to the DNA\u00a0<\/span><span class=\"glossaryTermLink\">upstream<\/span><span>\u00a0(5\u2032) of the gene at a specialized sequence called a\u00a0<\/span><span class=\"ontologyTermLink\">promoter<\/span><span> .<\/span><\/p>\n<h2 style=\"text-align: justify\">Prokaryotic Promoters<\/h2>\n<ul style=\"text-align: justify\">\n<li><span>The DNA sequence onto which the proteins and enzymes involved in transcription bind to initiate the process is called a<\/span><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_238_932\"><span>\u00a0<\/span><strong>promoter<\/strong><\/a><span>. Promoters usually exist upstream of the genes they regulate. The specific sequence of a promoter determines whether the corresponding gene is transcribed all of the time, some of the time, or hardly at all. The structure and function of a prokaryotic promoter is relatively simple\u00a0<\/span><\/li>\n<li><span style=\"font-size: 1em\"><strong>The -10 consensus sequence or the Pribnow box\u00a0<\/strong> : In prokaryotes, most genes have a sequence called the Pribnow box, with the <\/span><span class=\"ontologyTermLink\" style=\"font-size: 1em\">consensus sequence<\/span><span style=\"font-size: 1em\"><strong> TATAAT<\/strong> positioned about ten base pairs away from the site . This serves as the location of transcription initiation. Not all Pribnow boxes have this exact nucleotide sequence; these nucleotides are simply the most common ones found at each site.<\/span><\/li>\n<li><strong>The -35 consensus sequence :<\/strong> <span style=\"font-size: 1em\">Many genes also have the consensus sequence<\/span><strong><span style=\"font-size: 1em\"> TTGCCA <\/span><\/strong><span style=\"font-size: 1em\">at -35\u00a0 position, up<\/span><span style=\"text-align: initial;font-size: 1em\">stream of the start site<\/span><\/li>\n<li><strong><span class=\"glossaryTermLink\" style=\"text-align: initial;font-size: 1em\">Upstream element\u00a0 : <\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">an A-T rich region 40 to 60 nucleotides upstream that enhances the rate of transcription<\/span><\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"http:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter.jpg\" alt=\"Figure depicting the promoter elements in prokaryotes\" width=\"544\" height=\"243\" class=\"aligncenter size-full wp-image-268\" srcset=\"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter.jpg 544w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter-300x134.jpg 300w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter-65x29.jpg 65w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter-225x101.jpg 225w, https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-content\/uploads\/sites\/17\/2023\/03\/prokaryotic-promoter-350x156.jpg 350w\" sizes=\"(max-width: 544px) 100vw, 544px\" \/><\/p>\n<p style=\"text-align: center\"><span id=\"output\" class=\"outputbox\"><span style=\"color: #993366;background-color: #ffffff\">&#8220;Prokaryotic Promoter&#8221; Image from <a href=\"https:\/\/openstax.org\/books\/biology-2e\/pages\/15-2-prokaryotic-transcription\" style=\"background-color: #ffffff\"><em data-effect=\"italics\">Biology 2e<\/em>\u00a0(2nd edition), an OpenStax resource<\/a>\u00a0licensed under\u00a0<a href=\"http:\/\/creativecommons.org\/licenses\/by\/4.0\" target=\"_blank\" rel=\"noopener\" style=\"color: #993366;background-color: #ffffff\">CC BY 4.0<\/a><\/span><a><\/a><\/span><span><\/span><\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;font-size: 1em\">\u00a0The process of transcription starts with the binding of\u00a0 the RNA pol &#8220;holo<\/span><span class=\"glossaryTermLink\" style=\"text-align: initial;font-size: 1em\">enzyme<\/span><span style=\"text-align: initial;font-size: 1em\">&#8221; binding to the template DNA and\u00a0 unwinds\u00a0 the DNA <\/span><span class=\"ontologyTermLink\" style=\"text-align: initial;font-size: 1em\">double helix<\/span><span style=\"text-align: initial;font-size: 1em\"> in order to facilitate access to the gene. The sigma subunit conveys promoter specificity to RNA polymerase; that is, it instructs the\u00a0 RNA polymerase where to bind. There are a number of different sigma subunits that bind to different promoters. These sigma subunits assist in turning genes on and off as conditions change.<\/span><\/p>\n<p><span>The mRNA product is complementary to the template strand and is almost identical to the other DNA strand, called the\u00a0<\/span><strong>non-template strand<\/strong><span>, with the exception that RNA contains a uracil (U) in place of the thymine (T) found in DNA. Like DNA polymerase, RNA polymerase adds new nucleotides onto the 3\u2032-OH group of the previous nucleotide. This means that the growing mRNA strand is being synthesized in the 5\u2032 to 3\u2032 direction.\u00a0<\/span><\/p>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_238_923\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_238_923\"><div tabindex=\"-1\"><p>The process of Transcription and Translation occuring simultaneously. <\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_238_929\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_238_929\"><div tabindex=\"-1\"><p>Active enzyme comprising of an enzyme and its coenzyme<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_238_925\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_238_925\"><div tabindex=\"-1\"><p>Also called non coding strand . It is the DNA strand which acts as template for transcription<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_238_927\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_238_927\"><div tabindex=\"-1\"><p>Otherwise called as non coding strand .. This DNA strand does not serve as template for transcription<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_238_932\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_238_932\"><div tabindex=\"-1\"><p>The DNA sequence on to which the proteins and enzymes involved in transcription bind .to initiate the process of transcription<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":5,"menu_order":12,"template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"pb_show_title":"on","pb_short_title":"Prokaryotic Transcription","pb_subtitle":"Prokaryotic Transcription","pb_authors":["dr-v-malathi"],"pb_section_license":"cc-by-sa"},"chapter-type":[],"contributor":[61],"license":[54],"class_list":["post-238","chapter","type-chapter","status-publish","hentry","contributor-dr-v-malathi","license-cc-by-sa"],"aioseo_notices":[],"part":3,"_links":{"self":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/238","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/users\/5"}],"version-history":[{"count":40,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/238\/revisions"}],"predecessor-version":[{"id":996,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/238\/revisions\/996"}],"part":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/238\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/media?parent=238"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapter-type?post=238"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/contributor?post=238"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/license?post=238"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}