UHRF1, also named as ICBP90, NP95 and RNF106, is a putative E3 ubiquitin protein ligase. It may participate in methylation dependent transcriptional regulation. UHRF1 binds to inverted 5'CCAAT3' box 2 in the TOP2A promoter, and activates TOP2A expression. It is important for G1/S transition and may be involved in DNA repair and chromosomal stability. UHRF1's ability to repress its direct target gene expression is dependent on PHD (UHRF1) binding to unmodified H3R2.