| Cell cycle dependent phosphorylation of the RUNX 2 transcription factor by cdc 2 regulates endothelial cell proliferation . ^^^ Moreover , in vitro kinase assays using recombinant cdc 2 kinase showed that RUNX 2 was phosphorylated at Ser ( 451 ) . ^^^ The cdc 2 inhibitor roscovitine dose dependently inhibited in vivo RUNX 2 DNA binding activity during mitosis and the RUNX 2 mutant S451A exhibited lower DNA binding activity and reduced stimulation of anchorage independent growth relative to wild type RUNX 2 . ^^^ These results suggest for the first time that RUNX 2 phosphorylation by cdc 2 may facilitate cell cycle progression possibly through regulation of G ( 2 ) and M phases , thus promoting endothelial cell proliferation required for tumor angiogenesis . . ^^^ |