Cell
Volume 52, Issue 6, 25 March 1988, Pages 801-810
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Altered phosphorylation and activation of PP60c-src during fibroblast mitosis

https://doi.org/10.1016/0092-8674(88)90422-9Get rights and content

Abstract

At least half the pp60c-slc in NIH 3T3-derived c-src overexpressed cells is modified by novel threonine and, possibly, serine phosphorylation within its amino 16 kd region during mitosis. At the same time, the tryptic phosphopeptide containing Ser 17, the site of cyclic AMP-dependent phosphorylation, is either modified or dephosphorylated. While the amount of pp60c-src is not significantly altered, the in vitro-specific kinase activity of modified pp60c-src is enhanced 4- to 7-fold. Modified pp60c-src has the same tyrosine-containing tryptic phosphopeptides as pp60c-src from unsynchronized cells, indicating that activation is independent of Tyr 416/Tyr 527 phosphorylation. Electrophoretic mobility retardations indicated that endogenous pp60c-src and pp60v-src are similarly modified during mitosis. The modifications and enhanced activity disappear near the time of cell division. These results suggest that pp60c-src is regulated by and, in turn, may regulate mitosis-specific events in fibroblasts.

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    Current address: Amala Cancer Research Institute, Amala Nagar, Trichur 680553, Kerala, India.

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