The Expression and Characterization of Cyclin-dependent Kinase 6 during the Activation of Murine G0 T-Cells

Abstract

Recent evidence strongly suggest that the D type cy-clins with cdk4 and cdk6 form holoenzymes that regu-late cell cycle events earlier in G1 than cyclin E/cdk2 complexes which functions near the G1/S transition. In human T lymphocytes cdk6 has been shown to be the initial retinoblastoma protein kinase detectable at mid G1. Following activation of splenic derived murine G0T-cells, cdk6, cyclin D2 and D3 specific mRNAs were detected early in G1 and reached maximal levels prior to or near G1/S. The phosphorylation of retino-blastoma protein from T-cells was detected very early in G1 and was associated mainly with cdk6/cyclin D2 complexes which accounted for a minor portion of the total cellular cdk6 contained in the cytoplasmic frac-tion of T-cells and mostly in the catalytically inactive form.Keywords: D-Type Cyclin, Cdk6, Cell Cycle, T Lymphocytes