   3.1.13.B1 | physiological function |
yeast Rat1 is an essential nuclear protein. Within a complex with Rai1, the 5'-3' exoribonuclease Rat1 promotes termination of RNA polymerase II (RNAPII) on protein-coding genes. The 5'-3' exoribonuclease activity of Rat1 is essential for RNAPII termination. Rat1 forms a complex with Rai1 that stabilizes Rat1 and helps target 5' monophosphate RNA by its diphosphohydrolase activity. Within a complex with Rai1, the 5'-3' exoribonuclease Rat1 promotes termination of RNAPII on protein-coding genes, overview. RNAPII is prone to more effective termination by Rat1/Rai1 when its catalytic site is disrupted due to NTP misincorporation, implying that paused RNAPII, which is often found in vivo near termination sites, can adopt a similar configuration to Rat1/Rai1 and trigger termination. Rat1/Rai1 itself is not sufficient to terminate RNAPII in vitro. Multiple-mechanistic features contribute to Rat1-mediated termination of RNAPII. NTP misincorporation induces RNAPII pausing and enhances termination by Rat1/Rai1, Rat1/Rai1 more effectively terminates RNAPII when a non-cognate NTP (ATP, CTP or UTP), rather than cognate GTP. Exoribonuclease activity is required for Rat1 not only to approach RNAPII but also to accumulate a sufficient driving force to dislodge the polymerase from the DNA template |
751722 |
