RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
All three eukaryotic RNAPs require specific transcription factors, of which the TATA-binding protein is common to all. These proteins remain attached to the RNAP to guide the direction of RNA synthesis on the template DNA strand. Once RNA strand elongation is complete, the RNAP and associated proteins need to disassemble and release the mRNA transcript.
Unlike the termination signals encoded by bacterial genes, the protein-encoding genes transcribed by RNA Polymerase II lack specific sequences that direct the enzyme to terminate at precise locations. The most common termination pathway, known as the Poly(A) dependent termination, combines polyadenylation of the mRNA transcript with RNAP termination. Here, while the RNA Polymerase II continues to transcribe RNA, sometimes up to thousands of basepairs past the end of the gene sequence, the transcript is cleaved at an internal site. Thus the upstream part of the transcript is released and a polyadenine tail can be added to the 3' end of the cleaved transcript. The downstream cleavage product is digested by a 5'-exonuclease while it is still being transcribed by the RNA Polymerase II. When the 5'-exonuclease digests all of the remainder transcripts, it helps the RNAP to dissociate from its DNA template strand, thus completing the transcription.
진핵생물은 RNA 중합효소 I, II 및 III의 세 가지 다른 RNA 중합효소를 가지고 있습니다.그들은 구조적으로 서로 유사하고 원핵생물 RNA 중합효소와 공통된 특징을 공유하지만 다른 종류의 RNA를 전사합니다.
RNA 중합효소 I은 대부분의 리보솜 RNA 유전자를 전사하는 반면 RNA 중합효소 III는 tRNA 유전자, 일부 snRNA 및 기타 작은 RNA 유전자를 전사합니다.
단백질을 암호화하는 RNA 유전자의 대부분은 RNA 중합효소 II에 의해 전사됩니다.
RNA Polymerase II의 카르복시 말단 도메인은 효소 활성을 조절하는 여러 전사 인자에 대한 결합 부위 역할을 합니다. 이러한 인자의 결합은 이 영역의 인산화 패턴에 따라 달라집니다.
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