Phosphatase Family RTR1

Phosphatase Classification: Fold RTR1: Superfamily RTR1: Family RTR1

RTR1 is a phosphatase conserved in eukaryotes that regulates phosphorylation of the C-terminal domain (CTD) of RNA polymerase II.

Evolution

RTR1 is found in most eukaryotes. It is absent from the sponge genome, possibly due to incomplete genome assembly. It is single copy in most species including human (RPAP2). However, two copies are found in yeast (RTR1 and RTR2).

Domain

RTR1 proteins share a conserved catalytic domain. Yeast RTR1 has a C-terminal region that auto-inhibits the catalytic domain [1]. Human RPAP2 has a far longer tail of unknown function, though it is well conserved in most animals, and weakly conserved in plants. Nematode and Drosophila members lack this extended tail.

Function

Yeast RTR1 was shown to dephosphorylate serine-5 of CTD repeats of RNA pol II [2, 3], and similar activity was reported for human RPAP2 [4]. These findings were challenged by a later study of RTR1 from K. lactis [5]. But, more recent reports supports RTR1 dephosphorylates serine-5 as well as the newly described anti-termination tyrosine 1 residue of CTD repeats, and the lack of phosphatase activity shown in [5] is due to the absence of an identifiable step in the purification protocol, - the step removing inhibitory metal -, which resulted in an inactive protein [1].

References

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