MCMBP promotes the assembly of the MCM2–7 hetero-hexamer to ensure robust DNA replication in human cells

Abstract

The MCM2–7 hetero-hexamer is the replicative DNA helicase that plays a central role in eukaryotic DNA replication. In proliferating cells, the expression level of the MCM2–7 hexamer is kept high, which safeguards the integrity of the genome. However, how the MCM2–7 hexamer is assembled in living cells remains unknown. Here, we revealed that the MCM-binding protein (MCMBP) plays a critical role in the assembly of this hexamer in human cells. MCMBP associates with MCM3 which is essential for maintaining the level of the MCM2–7 hexamer. Acute depletion of MCMBP demonstrated that it contributes to MCM2–7 assembly using nascent MCM3. Cells depleted of MCMBP gradually ceased to proliferate because of reduced replication licensing. Under this condition, p53-positive cells exhibited arrest in the G1 phase, whereas p53-null cells entered the S phase and lost their viability because of the accumulation of DNA damage, suggesting that MCMBP is a potential target for killing p53-deficient cancers.

Cryo-EM structure of human hexameric MCM2-7 complex

“…Although it was reported that the interaction of yeast MCM2 3). Recently, it was reported that the MCM-binding protein (MCMBP) binds to Mcm3 through its N-terminal domain, which results in promoting the assembly of MCM2-7 complex in human cells (Saito et al, 2022). iScience Article However, we did not observe both MCMBP and Cdt1 during the preparation of MCM2-7 complex, indicating that the MCM2-7 hexamer is very stable once the six subunits assembled together.…”

“…Although it was reported that the interaction of yeast MCM2-7 with ATPγS promotes closure of Mcm2-Mcm5 gate and subsequently Cdt1 stabilizes the Mcm2-Mcm5 gate, only the open ring form of human MCM2-7 is observed after treatment of ATPγS in the absence of Cdt1 ( Figure 3 ). Recently, it was reported that the MCM-binding protein (MCMBP) binds to Mcm3 through its N-terminal domain, which results in promoting the assembly of MCM2-7 complex in human cells ( Saito et al., 2022 ). However, we did not observe both MCMBP and Cdt1 during the preparation of MCM2-7 complex, indicating that the MCM2-7 hexamer is very stable once the six subunits assembled together.…”

DNA replication: Mechanisms and therapeutic interventions for diseases

“…MCM proteins connecting with MCMBP is essential for maintaining the pool of functional MCM2‐7 hexamers. 128 , 129 …”

“…The MCM‐binding protein (MCMBP) is considered as a chaperone of MCM proteins to assist dynamic assembly of the MCM2‐7 hexamer and promotes MCM8‐9 for HR repair. MCM proteins connecting with MCMBP is essential for maintaining the pool of functional MCM2‐7 hexamers 128,129 …”

“…MCM proteins connecting with MCMBP is essential for maintaining the pool of functional MCM2-7 hexamers. 128,129 MCM10, components of the replication fork, loads to DNA after MCM2-7 complex settling down. MCM10 associates with Dna2 may function on the lagging strand during DNA replication, while Dna2 physically interacts with ATM at DNA damage sites.…”