Involvement of PGC7 and UHRF1 in the regulation of DNA methylation of the IG-DMR in the imprinted locus.

The gene dosage at the imprinted locus is critical for cell growth and development. A relatively high gene expression within the region, especially the active expression of , has been identified as the only reliable marker for cell pluripotency. The DNA methylation state of the IG-DNA methylated regions (DMR), which is located upstream of the gene, dominantly contributes to the control of gene expression in the locus. However, the precise mechanism underlying the regulation of DNA methylation in the IG-DMR remains largely unknown. Here, we use the F9 embryonal carcinoma cell line, a low pluripotent cell model, to identify the mechanism responsible for DNA methylation in the IG-DMR, and find that the interaction of PGC7 with UHRF1 is involved in maintaining DNA methylation and inducing DNA hypermethylation in the IG-DMR region. PGC7 and UHRF1 cooperatively bind in the IG-DMR to regulate the methylation of DNA and histones in this imprinted region. PGC7 promotes the recruitment of DNMT1 by UHRF1 to maintain DNA methylation in the IG-DMR locus. The interaction between PGC7 and UHRF1 strengthens their binding to H3K9me3 and leads to further enrichment of H3K9me3 in the IG-DMR by recruiting the specific histone methyltransferase SETDB1. Consequently, the abundance of H3K9me3 promotes DNMT3A to bind to the IG-DMR and increases DNA methylation level in this region. In summary, we propose a new mechanism of DNA methylation regulation in the IG-DMR locus and provide further insight into the understanding of the difference in expression levels between high and low pluripotent cells.