DBF4 Homolog B (DBF4B)

DBF4B encodes a regulator of the CDC7-like 1 protein, a serine-threonine kinase which links cell cycle regulation to genome duplication. This protein localizes to the nucleus and its expression is cell cycle-regulated. Alternative splicing of this gene results in two transcript variants encoding different isoforms. Additional transcript variants have been described, but their full length sequences have not been determined.The DBF4B-CDC7 protein complex displayed an in vitro kinase activity with a substrate preference for MCM2 and DBF4B itself was a substrate for CDC7. Kinase activity was not detected in CDC7 alone or in a protein complex containing a kinase-dead CDC7 mutant and DBF4B. Coimmunoprecipitation studies showed that DBF4B and DBF4 binding to CDC7 was mutually exclusive, with no formation of ternary complexes.