DNA size 5.48 kb; mRNA size 2674 bp; 10 exons.

546 amino acids; 60433 Da.
CDT1 contains cyclin binding motif 68-70 (3), and region for geminin interaction 150-190 (41). Cyclin-binding motif is the target for phosphorylation by cyclin A-dependent kinases, which results in the binding of Cdt1 to the F-box protein Skp2 and subsequent degradation. Interaction with geminin, a small regulatory protein active during S, G2, and M phases of the cell cycle, protects CDT1 from ubiquitin mediated degradation. Six natural variants, A135V (VAR-029163), R172C (VAR-029164), R234C (VAR-054504), T262A (VAR-054505), E456A (VAR-029165), and A537V (VAR-024408) have been reported.
Isoforms : There are three different isoforms, aApr07 (complete), bApr07 (partial), and cApr07 (COOH complete); all three isoforms putatively encode good proteins.
Post translational modifications : Phosphorylation occurs at position Thr²⁹, Ser³¹, Ser³¹⁸, Ser³⁷², and Ser³⁹⁴; however, phosphorylation does not affect binding to geminin.

Widely expressed, highly expressed in liver, thymus, and predominantly expressed in uterus and cervix of female reproductive system.

Nucleus.

The CDT1 protein is required for the formation of the pre-replicative complexes. CDT1 cooperates with CDC6 to promote loading of the mini-chromosome maintenance complex (MCM2-7) onto chromatin to form pre-replication complex necessary for the initiation of DNA replication. Moreover, CDT1 associates with the CDC7 kinase and recruits CDC45 to chromatin during S phase. Chromatin-bound CDT1 is first stabilized and subsequently displaced by CDC7 activity, which ensures timely execution of DNA replication. CDT1 is also a potential oncogene; overexpression of CDT1 promotes rereplication and generates a DNA damage senescence and response that activates the antitumor barriers of senescence and apoptosis.
Regulation : CDT1 is regulated either by cell cycle dependent proteolysis during S and G2 phase or by geminin. Proteolysis of CDT1 during S and G2 phases is dependent on the CDK2 -cyclin A mediated phosphorylation of CDT1 and subsequent proteolysis by SCF-Skp2 complex. CDT1 activity is also inhibited by the tight binding of geminin that blocks the ability of CDT1 to load MCM2-7 onto DNA.

The percent identity below represents identity of CDT1 over an aligned region in UniGene.
-Mus musculus : 82 % (percent identity)
-Bos taurus : 76.2 %
-Canis familiaris : 74.54 %
-Rattus norvegicus : 74.49 %
-Xenopus laevis : 62.5 %
-Danio rerio : 60 %.

The RRL --->AAA mutation in the cyclin binding motif abolishes the binding of Cyclin A-dependent protein kinases with CDT1.