S1_RNAPII_Rpb7: Eukaryotic RNA polymerase II (RNAPII) Rpb7 subunit C-terminal S1 domain. RNAPII is composed of 12 subunits (Rpb1-12). Rpb4 and Rpb7 form a heterodimer that associate with the RNAPII core. Rpb7 is a homolog of the Rpc25 of RNA polymerase III, RpoE of the archaeal RNA polymerase, and Rpa43 of eukaryotic RNA polymerase I. Rpb7 has two domains, an N-terminal ribonucleoprotein (RNP) domain and a C-terminal S1 domain, both of which bind single-stranded RNA. It is possible that the S1 domain interacts with the nascent RNA transcript, assisted by the RNP domain. In yeast, Rpb4/Rpb7 is necessary for promoter-directed transcription initiation. They also play a role in regulating transcription-coupled repair in the Rad26-dependent pathway, in efficient mRNA export, and in transcription termination.
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