{"id":274,"date":"2023-03-11T17:49:55","date_gmt":"2023-03-11T17:49:55","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/?post_type=chapter&p=274"},"modified":"2023-04-07T09:54:28","modified_gmt":"2023-04-07T09:54:28","slug":"prokaryotic-transcription-elongation-termination","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/chapter\/prokaryotic-transcription-elongation-termination\/","title":{"raw":"Prokaryotic Transcription - Elongation & Termination","rendered":"Prokaryotic Transcription – Elongation & Termination"},"content":{"raw":"
\r\n

Elongation<\/strong><\/h3>\r\n<\/div>\r\n
\r\n
\r\n
\r\n

Once transcription is initiated, the DNA double helix unwinds and RNA polymerase reads the template strand. Elongation phase begins with the release of the\u00a0<\/span>\u03c3<\/em>\u00a0<\/span>subunit from the polymerase. The dissociation of<\/span>\u00a0<\/span>\u03c3<\/em>\u00a0<\/span>allows the core enzyme to proceed along the DNA template, synthesizing mRNA in the 5\u2032 to 3\u2032 direction .<\/span><\/p>\r\n

Nucleotides\u00a0 are added to the 3\u2032 end of the growing chain . At a temperature of 370 <\/sup>C new nucleotides are added at an estimated rate of about 42-54 nucleotides per second in bacteria. As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it. The base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely.<\/span><\/p>\r\n\"Picture\r\n

\"Process of transcription \"<\/span><\/a>\u00a0by\u00a0NHS National Genetics and Genomics Education Centre.\u00a0<\/a><\/a><\/a>is licensed under\u00a0CC BY 2.0<\/a>\u00a0<\/span><\/span><\/p>\r\n\r\n

Termination<\/h1>\r\n

Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals namely :<\/p>\r\n\r\n

    \r\n \t
  1. Rho-dependent or Extrinsic termination : <\/strong>Termination is controlled by the rho protein.The rho protein tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. As a result, the rho protein collides with the polymerase. Rho unwinds the DNA-RNA\u00a0<\/span>hybrid<\/span>\u00a0formed during transcription<\/span> and releases the mRNA from the transcription bubble.<\/li>\r\n \t
  2. Rho-independent or Intrinsic termination<\/strong>\u00a0<\/span>is controlled by\u00a0 C\u2013G nucleotide sequences in the DNA template strand at the end of the gene being transcribed. Due to the self complementary nature of the C-G nucleotides . The mRNA folds back on itself, and form a stable\u00a0<\/span>hairpin<\/strong> . This <\/span>causes the polymerase to stall and\u00a0 it begins to transcribe a region rich in A\u2013T nucleotides. The complementary U\u2013A region of the mRNA transcript forms only a weak interaction with the template DNA. This fact together\u00a0 with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.<\/li>\r\n<\/ol>\r\n

    Upon termination, the process of transcription is complete. By the transcription would end the prokaryotic transcript would\u00a0 have already commenced the\u00a0 \u00a0synthesis of numerous copies of the encoded protein .<\/p>\r\n\r\n<\/div>\r\n

    \"Picture<\/p>\r\n

    \"Prokaryotic Terminators \"<\/a>\u00a0by\u00a0Oalnafo via Wikimedia Commons<\/a><\/a><\/a>\u00a0is licensed under\u00a0CC BY-SA 3.0<\/a><\/span><\/p>\r\n\r\n<\/div>\r\n<\/div>","rendered":"

    \n

    Elongation<\/strong><\/h3>\n<\/div>\n
    \n
    \n
    \n

    Once transcription is initiated, the DNA double helix unwinds and RNA polymerase reads the template strand. Elongation phase begins with the release of the\u00a0<\/span>\u03c3<\/em>\u00a0<\/span>subunit from the polymerase. The dissociation of<\/span>\u00a0<\/span>\u03c3<\/em>\u00a0<\/span>allows the core enzyme to proceed along the DNA template, synthesizing mRNA in the 5\u2032 to 3\u2032 direction .<\/span><\/p>\n

    Nucleotides\u00a0 are added to the 3\u2032 end of the growing chain . At a temperature of 370 <\/sup>C new nucleotides are added at an estimated rate of about 42-54 nucleotides per second in bacteria. As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it. The base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely.<\/span><\/p>\n

    \"Picture<\/p>\n

    “Process of transcription “<\/span><\/a>\u00a0by\u00a0NHS National Genetics and Genomics Education Centre.\u00a0<\/a><\/a><\/a>is licensed under\u00a0CC BY 2.0<\/a>\u00a0<\/span><\/span><\/p>\n

    Termination<\/h1>\n

    Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals namely :<\/p>\n

      \n
    1. Rho-dependent or Extrinsic termination : <\/strong>Termination is controlled by the rho protein.The rho protein tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. As a result, the rho protein collides with the polymerase. Rho unwinds the DNA-RNA\u00a0<\/span>hybrid<\/span>\u00a0formed during transcription<\/span> and releases the mRNA from the transcription bubble.<\/li>\n
    2. Rho-independent or Intrinsic termination<\/strong>\u00a0<\/span>is controlled by\u00a0 C\u2013G nucleotide sequences in the DNA template strand at the end of the gene being transcribed. Due to the self complementary nature of the C-G nucleotides . The mRNA folds back on itself, and form a stable\u00a0<\/span>hairpin<\/strong> . This <\/span>causes the polymerase to stall and\u00a0 it begins to transcribe a region rich in A\u2013T nucleotides. The complementary U\u2013A region of the mRNA transcript forms only a weak interaction with the template DNA. This fact together\u00a0 with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.<\/li>\n<\/ol>\n

      Upon termination, the process of transcription is complete. By the transcription would end the prokaryotic transcript would\u00a0 have already commenced the\u00a0 \u00a0synthesis of numerous copies of the encoded protein .<\/p>\n<\/div>\n

      \"Picture<\/p>\n

      “Prokaryotic Terminators “<\/a>\u00a0by\u00a0Oalnafo via Wikimedia Commons<\/a><\/a><\/a>\u00a0is licensed under\u00a0CC BY-SA 3.0<\/a><\/span><\/p>\n<\/div>\n<\/div>\n","protected":false},"author":5,"menu_order":13,"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 - Elongation & termination","pb_subtitle":"Prokaryotic Transcription - Elongation & termination","pb_authors":["dr-v-malathi"],"pb_section_license":"cc-by-sa"},"chapter-type":[],"contributor":[61],"license":[54],"class_list":["post-274","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\/274","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":19,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/274\/revisions"}],"predecessor-version":[{"id":994,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapters\/274\/revisions\/994"}],"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\/274\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/media?parent=274"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/pressbooks\/v2\/chapter-type?post=274"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/contributor?post=274"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/wp-json\/wp\/v2\/license?post=274"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}