Chromatin Licensing And DNA Replication Factor 1 (CDT1)

CDT1 is a key licensing factor which, along with the protein Cdc6, functions to license DNA by forming the pre-replicative complex (pre-RC). Its activity during the cell cycle is tightly regulated by its association with the protein geminin, which both inhibits Cdt1 activity during S phase in order to prevent re-replication of DNA and prevents it from ubiquitination and subsequent proteolysis.

human CDT1 is a 65-kD protein that contains 546 amino acids and coimmunoprecipitates with geminin. Inhibition of DNA replication by geminin in cell-free cDNA replication extracts could be reversed by the addition of excess CDT1. In the normal cell cycle, CDT1 is present only in G1 and S phases, whereas geminin is present in S and G2 phases.