Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.

摘要: Phosphorylation of the retinoblastoma protein (pRB) is assumed to regulate its growth-controlling function. Moreover, hypophosphorylated and hyperphosphorylated forms pRB can be distinguished by virtue distinct affinities with which they bind cell nucleus. This property allows identification individual nuclei that contain in one or other form. We show here after cells emerge from a quiescent (G0) state, conversion their complement into form occurs late G1, preceding entry S phase several hours. Thus, contrary earlier reports, phosphorylation not co-ordinated G1-S transition may directly it. A set phosphopeptides found exclusively those loose nuclear association characteristic pRB. Another both forms. suggests existence patterns are associated different subsets molecules. conclude substantial exists G1 even prior hyperphosphorylation point. Cyclin-dependent kinases cause liberation vitro. members this kinase family therefore likely involved change affinity vivo changes functioning.