Cell cycle-dependent phosphorylation of the RUNX2 transcription factor by cdc2 regulates endothelial cell proliferation.
RUNX2 is a member of the runt family of DNA-binding transcription factors. RUNX2 mediates endothelial cell migration and invasion during tumor angiogenesis and is expressed in metastatic breast and prostate tumors. Our published studies showed that RUNX2 DNA-binding activity is low during growth arrest, but elevated in proliferating endothelial cells. To investigate its role in cell proliferation and cell cycle regulation, RUNX2 was depleted in human bone marrow endothelial cells using RNA interference. Specific RUNX2 depletion inhibited DNA-binding activity as measured by electrophoretic mobility shift assay resulting in inhibition of cell proliferation. Cells were synchronized at the G(1)/S boundary with excess thymidine or in mitosis (M phase) with nocodazole. Endogenous or ectopic RUNX2 activity was maximal at late G(2) and during M phase. Inhibition of RUNX2 expression by RNA interference delayed entry into and exit out of the G(2)/M phases of the cell cycle. RUNX2 was coimmunoprecipitated with cyclin B1 in mitotic cells, which further supported a role for RUNX2 in cell cycle progression. Moreover, in vitro kinase assays using recombinant cdc2 kinase showed that RUNX2 was phosphorylated at Ser(451). The cdc2 inhibitor roscovitine dose dependently inhibited in vivo RUNX2 DNA-binding activity during mitosis and the RUNX2 mutant S451A exhibited lower DNA-binding activity and reduced stimulation of anchorage-independent growth relative to wild type RUNX2. These results suggest for the first time that RUNX2 phosphorylation by cdc2 may facilitate cell cycle progression possibly through regulation of G(2) and M phases, thus promoting endothelial cell proliferation required for tumor angiogenesis.
Qiao
Meng
M
Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA.
Shapiro
Paul
P
Fosbrink
Matthew
M
Rus
Horea
H
Kumar
Rakesh
R
Passaniti
Antonino
A
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002469:Cell Separation; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism*; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D004247:DNA / Q000378:metabolism; D015536:Down-Regulation; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D000939:Epitopes; D005434:Flow Cytometry; D016193:G1 Phase; D016195:G2 Phase; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D009362:Neoplasm Metastasis; D010766:Phosphorylation; D011485:Protein Binding; D034622:RNA Interference; D016196:S Phase; D013936:Thymidine / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; D050659:Core Binding Factor Alpha 1 Subunit; D019926:Cyclin B; D056744:Cyclin B1; D000939:Epitopes; D014157:Transcription Factors; D004247:DNA; D016203:CDC2 Protein Kinase; D013936:Thymidine