Transcription factor involved in osteoblastic differentiation and skeletal morphogenesis. Essential for the maturation of osteoblasts and both intramembranous and endochondral ossification. CBF binds to the core site, 5'-PYGPYGGT-3', of a number of enhancers and promoters, including murine leukemia virus, polyomavirus enhancer, T-cell receptor enhancers, osteocalcin, osteopontin, bone sialoprotein, alpha 1(I) collagen, LCK, IL-3 and GM-CSF promoters. Inhibits KAT6B-dependent transcriptional activation (By similarity). In osteoblasts, supports transcription activation: synergizes with SPEN/MINT to enhance FGFR2-mediated activation of the osteocalcin FGF-responsive element (OCFRE). Heterodimer of an alpha and a beta subunit. The alpha subunit binds DNA as a monomer and through the Runt domain. DNA-binding is increased by heterodimerization. Interacts with XRCC6 (Ku70) and XRCC5 (Ku80). Interacts with CCNB1, KAT6A and KAT6B (By similarity). Interacts with HIVEP3. Interacts with IFI204. Interaction with SATB2; the interaction results in enhanced DNA binding and transactivation by these transcription factors. Binds to HIPK3. Interacts (isoform 3) with DDX5. Interacts with FOXO1 (via a C-terminal region); the interaction inhibits RUNX2 transcriptional activity towards BGLAP. Interacts with FOXP3 (By similarity). Interacts with TMEM119 (PubMed:21239498). Interacts with OLFM2 (By similarity). Additional isoforms seem to exist. Found in thymus and testis, T-cell lines but not in B-cell lines. Isoform 2 is exclusively found in bone, particularly in osteoblasts; isoforms 3 and 4 are expressed in T-cell lines; isoforms 5, 6, 7, 8 and 9 can be found in osteoblasts and osteosarcoma cell lines. Expression occurs early during skeletal development and is restricted to cells of the mesenchymal condensations and of the osteoblast lineage. Expression of isoform 2 in the embryo reaches a peak at 12.5 dpc. A proline/serine/threonine rich region at the C-terminus is necessary for transcriptional activation of target genes and contains the phosphorylation sites. Phosphorylated; probably by MAP kinases (MAPK). Phosphorylation by HIPK3 is required for the SPEN/MINT and FGF2 transactivation during osteoblastic differentiation. Phosphorylation at Ser-537 by CDK1 promotes endothelial cell proliferation required for tumor angiogenesis probably by facilitating cell cycle progression (By similarity).