Kinetics of DNA methylation inheritance by the Dnmt1-including complexes during the cell cycle

P-LISA, sequential chromatin immunoprecipitation and quantitative methylation specific PCR revealed that the Dnmt1/PCNA/UHRF1-including complexes are mainly formed and recruited on DNA during the S-phase of cell cycle, while the formation and the DNA recruitment of several Dnmt1/transcription factors-including complexes are not S-phase dependent but are G0/G1 and/or G2/M phases dependent.Our data confirm that DNA methylation inheritance occurs in S-phase, and demonstrate that DNA methylation inheritance can also occur in G0/G1 and G2/M phases of the cell cycle.DNA methylation playing a crucial role in the regulation of gene transcription, genomic imprinting, genomic stability, and × chromosome inactivation, its inheritance is essential for the cellular biology and viability because aberrant DNA methylation and targeted disruption of DNA methyltransferase enzymes result in tumorigenicity, lethality or mitotic catastrophe [1-5]. We and others have recently demonstrated that the majority of genomic methylation inheritance is catalyzed by the Dnmt1/PCNA/UHRF1-including complex since its disruption promote global DNA hypomethylation [4,6-8]. Nevertheless, other Dnmt-including complexes can catalyze the genomic DNA methylation inheritance. More generally, the majority of Dnmt1-including complexes are implicated in the inheritance of DNA methylation since Dnmt1 is responsible for maintaining genomic methylation, even if other Dnmt-including complexes could catalyzed maintenance DNA methylation reactions [9,10].Recently, we reported that the Dnmt1/transcription factors-including complexes act as an alternative mechanism of DNA methylation inheritance to the mechanism performed by the Dnmt1/PCNA/UHRF1-including complex [11]. To complement this point, we here investigated the dynamic of formation of several of these complexes during the cell cycle. Proximity Ligation In Situ Assay (P-LISA) and ApoTome technology confirmed that the Dnmt1/PCNA/UHRF1-including complex is mainly