Linked Life Data

15467457

Source:http://linkedlifedata.com/resource/pubmed/id/15467457

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
2004-12-21
pubmed:abstractText
It is thought that G(1) cyclin/CDK mediated phosphorylation of pocket proteins from mid G(1) to mitosis is reversed via dephosphorylation in mitosis. We examined the mechanisms involved in the unexpectedly rapid dephosphorylation of the pocket proteins induced via inhibition of cellular protein synthesis by cycloheximide (CHX) as well as direct inhibition of CDKs by flavopiridol. CHX and flavopiridol-induced dephosphorylation of pocket proteins is attributable to inactivation of D-type cyclin/CDKs and G(1)/S CDKs, respectively, which unmasks a phosphatase activity that targets the three pocket proteins apparently throughout the cell cycle. Treatment of cells with phosphatase inhibitors at concentrations selective for PP2A inhibition prevents CHX and flavopiridol-mediated dephosphorylation of pocket proteins in vivo. Also, ectopic expression of SV40 small t antigen, which inhibits PP2A via disruption of trimeric PP2A holoenzymes, delays CHX-induced pocket protein dephosphorylation. Moreover, dephosphorylation of p130 and p107 in cell extracts is inhibited by concentrations of okadaic acid known to inhibit PP2A, but not PP1. Finally, the PP2A catalytic subunit (PP2A/C) specifically interacts with both p130 and p107 in quiescent cells as well as cells progressing throughout the cell cycle. Together, these results demonstrate that the overall phosphorylation state of pocket proteins is determined, at least in part, by a dynamic equilibrium between CDKs and PP2A, or a closely related PP2A-like enzyme. These findings have important implications, as cell cycle or checkpoint-dependent inhibition of CDK activities counteracted by an active PP2A should have imminent effects on the phosphorylation state and activities of pocket proteins.
pubmed:grant
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
1551-4005
pubmed:author
pubmed:issnType
Electronic
pubmed:volume
3
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1320-30
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
A dynamic equilibrium between CDKs and PP2A modulates phosphorylation of pRB, p107 and p130.
pubmed:affiliation
Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural