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Negative regulation of mitosis in fission yeast by catalytically inactive pyp1 and pyp2 mutants

Hannig, G., Ottilie, S., Erikson, R.L.
Proceedings of the National Academy of Sciences of the United States of America 1994 v.91 no.21 pp. 10084-10088
Saccharomycetales, mitosis, mutants, phosphoprotein phosphatase, Schizosaccharomyces pombe, protein-tyrosine-phosphatase
The Schizosaccharomyces pombe genes pyp1+ and pyp2+ encode protein tyrosine phosphatases (PTPases) that act as negative regulators of mitosis upstream of the wee1+/mik1+ pathway. Here we provide evidence that pyp1+ and pyp2+ function independently of cdr1+(nim1+) in the inhibition of mitosis and that the wee1 kinase is not a direct substrate of either PTPase. In a pyp1::ura4 cdc25-22 genetic background, overexpression of either the N-terminal domain of pyp1+ or a catalytically inactive mutant, pyp1C470S, causes cell cycle arrest. This phenotype reverses the suppression of a cdc25 temperature-sensitive mutation at 35 degrees caused by a pyp1 disruption. Furthermore, pyp1C470S and a catalytically inactive mutant of pyp2, pyp2C630S, induce mitotic delay as do their wild-type counterparts. Analysis of pyp1+ and pyp2+ further reveals that the in vitro PTPase activity of pyp1 and pyp2, as well as their biological activity, is dependent on the presence of N-terminal sequences that are not normally considered part of PTPase catalytic domains.