Specific replication factors are targeted by different genotoxic agents to inhibit replication

Direct visualization of replication dynamics in early zebrafish embryos

We analyzed DNA replication in early zebrafish embryos. The replicating DNA of whole embryos was labeled with the thymidine analog 5-ethynyl-2'-deoxyuridine (EdU), and spatial regulation of replication sites was visualized in single embryo-derived cells. The results unveiled uncharacterized replication dynamics during zebrafish early embryogenesis.

CRL4-DDB1-VPRBP ubiquitin ligase mediates the stress triggered proteolysis of Mcm10

When mammalian cells experience radiation insult, DNA replication is stalled to prevent erroneous DNA synthesis. UV-irradiation triggers proteolysis of Mcm10, an essential human replication factor, inhibiting the ongoing replication. Here, we report that Mcm10 associates with E3 ubiquitin ligase comprising DNA damage-binding protein, DDB1, cullin, Cul4 and ring finger protein, Roc1. Depletion of DDB1, Roc1 or Cul4 abrogates the UV-triggered Mcm10 proteolysis, implying that Cul4-Roc1-DDB1 ubiquitin ligase mediates Mcm10 downregulation. The purified Cul4-Roc1-DDB1 complex ubiquitinates Mcm10 in vitro, proving that Mcm10 is its substrate. By screening the known DDB1 interacting proteins, we discovered that VprBP is the substrate recognition subunit that targets Mcm10 for degradation. Hence, these results establish that Cul4-DDB1-VprBP ubiquitin ligase mediates the stress-induced proteolysis of replication factor, Mcm10.