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Journal Article

The mRNA transcription/processing factor Ssu72 is a potential tyrosine phosphatase

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Meinhart,  Anton
mRNA Processing, Max Planck Institute for Medical Research, Max Planck Society;
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Meinhart, A., Silberzahn, T., & Cramer, P. (2003). The mRNA transcription/processing factor Ssu72 is a potential tyrosine phosphatase. The Journal of Biological Chemistry, 278(18), 15917-15921. doi:10.1074/jbc.M301643200.


Cite as: http://hdl.handle.net/21.11116/0000-0000-3CBC-A
Abstract
Ssu72 is an essential and highly conserved protein involved in mRNA transcription and 3'-end processing. The biochemical function of Ssu72 was so far unknown. We report here evidence that Ssu72 is a phosphatase that resembles protein tyrosine phosphatases (PTPases). First, recombinant Ssu72 cleaves the phosphotyrosine analogue p-nitrophenylphosphate, and this catalytic activity is impaired by PTPase-inhibiting agents. Second, the Ssu72 sequence contains the CX(5)R signature motif of PTPases; mutation of the catalytic cysteine in this motif abolishes Ssu72 activity in vitro and has been shown to confer lethality in vivo. Third, secondary structure prediction and site-directed mutagenesis predict that Ssu72 adopts the fold of PTPases of the low molecular weight family. Distinguishing features, such as a short "aspartate loop" at the active site, suggest however that Ssu72 is the founding member of a new phosphatase subfamily. The novel Ssu72 activity may regulate coupling events during mRNA biogenesis.