Phosphatase Family SSU72

Function

The phosphatase activity of Ssu72 is important for Pol II transcription and termination and for gene looping. It catalyzes CTD Serine-5 dephosphorylation in association with the Pta1 component of the CPF complex. In yeast, Ssu72 is required for pre-mRNA 3’-end cleavage, but so far no evidence exists implicating mammalian Ssu72 in that processing [1] [2].

Evolution

Ssu72 can be found in all the unikonts (animals, choanoflagellates, fungi, and amoebozoan), plants/algae, Heterokonts, Trichomonas vaginalis (but not Giardia or Trypanasoma or Leishmania).

Comparison of the catalytic site with LMW-PTP

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Ssu72

LMW-PTP

Sequence logo of catalytic site of Ssu72 and LMW-PTP. The logo of Ssu72 was built from 33 sequences, and that of LMW-PTP from 42 sequences including five known prokaryotic LMW-PTPs.

Reference

1. Krishnamurthy S, He X, Reyes-Reyes M, Moore C, and Hampsey M. Ssu72 Is an RNA polymerase II CTD phosphatase. Mol Cell. 2004 May 7;14(3):387-94. DOI:10.1016/s1097-2765(04)00235-7 |
2. Xiang K, Nagaike T, Xiang S, Kilic T, Beh MM, Manley JL, and Tong L. Crystal structure of the human symplekin-Ssu72-CTD phosphopeptide complex. Nature. 2010 Oct 7;467(7316):729-33. DOI:10.1038/nature09391 |