Phosphatase Family SSU72

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Phosphatase Classification: Superfamily CC2: Family SSU72

SSU72 is a nearly pan-eukaryotic phosphatase of the RNA polymerase C-terminal domain.


SSU72 is found in most eukaryotes, but is lost in most excavates and some chromalveolates. It is usually present in one copy, but humans also have 8 SSU72 retrogenes of unknown function.

Domain Architecture

SSU72 consist of just a phosphatase domain, with no N- or C-terminal extensions.


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].


  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 | PubMed ID:15125841 | HubMed [Krish04]
  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 | PubMed ID:20861839 | HubMed [Xiang10]
All Medline abstracts: PubMed | HubMed