Interaction of p58PITSLRE, a G2/M-specific Protein Kinase, with Cyclin D3

The p58 PITSLRE is a p34 cdc2 -related protein kinase that plays an important role in normal cell cycle progression. Elevated expression of p58 PITSLRE in eukaryotic cells prevents them from undergoing normal cytokinesis and appears to delay them in late telophase. To investigate the molecular mechanism of p58 PITSLRE action, we used the yeast two-hybrid system, screened a human fetal liver cDNA library, and identified cyclin D3 as an interacting partner of p58 PITSLRE . In vitro binding assay, in vivo coimmunoprecipitation, and immunofluorescence cell staining further confirmed the association of p58 PITSLRE with cyclin D3. This binding was observed only in the G 2 /M phase but not in the G 1 /S phase of the cell cycle; meanwhile, no interaction between p110 PITSLRE and cyclin D3 was observed in all the cell cycle. The overexpression of cyclin D3 in 7721 cells leads to an exclusively accumulation of p58 PITSLRE in the nuclear region, affecting its cellular distribution. Histone H1 kinase activity of p58 PITSLRE was greatly enhanced upon interaction with cyclin D3. Furthermore, kinase activity of p58 PITSLRE was found to increase greatly in the presence of cyclin D3 using a specific substrate, β-1,4-galactosyltransferase 1. These data provide a new clue to our understanding of the cellular function of p58 PITSLRE and cyclin D3.