Claspin
Domain
The C-terminus of the protein contains 3 potential CHEK1-binding motifs (CKB motifs). Potential phosphorylation sites within CKB motif 1 and CKB motif 2 are required for interaction with CHEK1.
The acidic patch region is required for normal DNA replication. Interacts with the N-terminal segments and inhibits binding to DNA and PCNA. Mediates the interaction with the kinase CDC7 as well as some replisome factors and DNA polymerases.
Function
Required for checkpoint mediated cell cycle arrest in response to inhibition of DNA replication or to DNA damage induced by both ionizing and UV irradiation (PubMed:12766152, PubMed:15190204, PubMed:15707391, PubMed:16123041). Adapter protein which binds to BRCA1 and the checkpoint kinase CHEK1 and facilitates the ATR-dependent phosphorylation of both proteins (PubMed:12766152, PubMed:15096610, PubMed:15707391, PubMed:16123041). Also required to maintain normal rates of replication fork progression during unperturbed DNA replication. Binds directly to DNA, with particular affinity for branched or forked molecules and interacts with multiple protein components of the replisome such as the MCM2-7 complex and TIMELESS (PubMed:15226314, PubMed:34694004, PubMed:35585232). Important for initiation of DNA replication, recruits kinase CDC7 to phosphorylate MCM2-7 components (PubMed:27401717).
Post-translational modifications
Phosphorylated. Undergoes ATR-dependent phosphorylation by CHEK1 during activation of DNA replication or damage checkpoints. Phosphorylation by CSNK1G1/CK1 promotes CHEK1 binding (PubMed:12766152, PubMed:15096610, PubMed:16963448, PubMed:21680713). Phosphorylated by CDC7 during DNA replication, phosphorylation inhibits interaction between the acidic patch and N-terminal segments leading to increased binding to DNA and PCNA (PubMed:27401717).
Ubiquitinated by the anaphase promoting complex/cyclosome (APC/C) during G1 phase, leading to its degradation by the proteasome. Ubiquitination is mediated via its interaction with FZR1/CDH1. Following DNA damage, it is deubiquitinated by USP28 in G2 phase, preventing its degradation.
Proteolytically cleaved by caspase-7 (CASP7) in response to apoptosis, leading to its inactivation.
Sequence Similarities
Belongs to the claspin family.
Cellular localization
- Nucleus
Alternative names
Claspin, hClaspin, CLSPN