Plasmids containing RNF125 and MCM2-7 were purchased from Shanghai Cell Researcher Biotech Co., Ltd. and inserted into empty vectors, which were purchased from Cell Researcher Biotech Co., Ltd.), such as pCDH, pCDNA3.0-Myc, pET22b or pGEX4T-1. Briefly, pCDH-MCM2/MCM3/MCM6/MCM7/RNF125, pCDNA3.0-RNF126-Myc, pET22b-MCM2/MCM3/MCM6/MCM7/RNF125/UBA1/UBCH5A/catalytic core of human ubiquitin specific peptidase 2 (Usp2cc) and pGEX4T-1-MCM6/RNF125 were generated. Mutations were generated in plasmids containing RNF125 or MCM6 by site-directed mutagenesis as previously described (20 (link)). Short hairpin RNAs (shRNAs) inserted into the Plko.1 vector targeting RNF125 and MCM2, MCM3, MCM6 and MCM7 were also purchased from Shanghai Cell Researcher Biotech Co., Ltd., and the specific sequences of these shRNAs are shown in Table I.