Cyclin E and cyclin A as candidates for the restriction point protein.
Progression of cells into S phase is proposed to be determined by accumulation of a labile protein (the restriction point protein R; A. B. Pardee, Proc. Natl. Acad. Sci. USA, 71: 1286-1290, 1974). We report here that cyclin E and cyclin A proteins as well as their dependent histone H1 kinases satisfy all of the criteria for the R protein, which includes late G1 phase increase, an excess delay of appearance after inhibition of protein synthesis in nontransformed cells, and a faster recovery in transformed cells. We suggest that the molecular basis of the R protein could be cyclin production and inactivation.
Dou
Q P
QP
Division of Cell Growth and Regulation, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Levin
A H
AH
Zhao
S
S
Pardee
A B
AB
D016475:3T3 Cells; D000818:Animals; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D002460:Cell Line; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000187:drug effects / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D016193:G1 Phase; D051379:Mice; D006656:Protamine Kinase / Q000187:drug effects / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D016196:S Phase / Q000502:physiology*; D013997:Time Factors
D016213:Cyclins; D003513:Cycloheximide; D011494:Protein Kinases; D006656:Protamine Kinase; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases