Identification of UHRF1/2 as new N-methylpurine DNA glycosylase-interacting proteins.

N-methylpurine DNA glycosylase (MPG), a DNA repair enzyme, functions in the DNA base excision repair (BER) pathway. Aberrant over-expression of MPG in various cancers suggests an important role of MPG in carcinogenesis. Identification of MPG-interacting proteins will help to dissect the molecular link between MPG and cancer development. In the present study, using immunoprecipitation coupled with mass spectrometry (IP/MS), we screened ubiquitin-like, containing PHD and RING finger domains 1 (UHRF1), an essential protein required for the maintenance of DNA methylation, as a MPG-interacting protein. Endogenous co-immunoprecipitation assay in cancer cells confirmed that UHRF1 interacted with MPG in a p53 status-independent manner. Confocal microscopy showed that endogenous MPG and UHRF1 were co-localized in the nucleoplasm. Furthermore, co-immunoprecipitation assay indicated that UHRF2, the homolog of UHRF1, could also interact with MPG. These results show that MPG and the UHRF family of proteins interact, thus providing a functional linkage between MPG and UHRF1/2.