Login processing...

Trial ends in Request Full Access Tell Your Colleague About Jove

8.9: Eukaryotic RNA Polymerases

JoVE Core
Molecular Biology

A subscription to JoVE is required to view this content. Sign in or start your free trial.

Eukaryotic RNA Polymerases

8.9: Eukaryotic RNA Polymerases

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.

Lectura sugerida


Eukaryotic RNA Polymerases RNA Polymerase I RNA Polymerase II RNA Polymerase III Ribosomal RNA Genes TRNA Genes SnRNA Small RNA Genes Protein-encoding RNA Genes Carboxy-terminal Domain Transcription Factors Phosphorylation Pattern TATA Box General Transcription Factors Transcription Factor 2 (TFII) TFIID TATA Box Binding Protein (TBP) TFIIA TFIIB TFIIF TFIIE TFIIH

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter