first Tudor domain found in ubiquitin-like PHD and RING finger domain-containing protein 2 (UHRF2) and similar proteins
UHRF2, also called Np95/ICBP90-like RING finger protein (NIRF), Np95-like RING finger protein, nuclear protein 97, nuclear zinc finger protein Np97, RING finger protein 107, or E3 ubiquitin-protein ligase UHRF2, was originally identified as a ubiquitin ligase acting as a small ubiquitin-like modifier (SUMO) E3 ligase that enhances zinc finger protein 131 (ZNF131) SUMOylation but does not enhance ZNF131 ubiquitination. It also ubiquitinates PCNP, a PEST-containing nuclear protein. UHRF2 also functions as a nuclear protein involved in cell-cycle regulation and has been implicated in tumorigenesis. It interacts with cyclins, CDKs, p53, pRB, PCNA, HDAC1, DNMTs, G9a, methylated histone H3 lysine 9, and methylated DNA. It interacts with the cyclin E-CDK2 complex, ubiquitinates cyclins D1 and E1, induces G1 arrest, and is involved in the G1/S transition regulation. Furthermore, UHRF2 is a direct transcriptional target of the transcription factor E2F-1 in the induction of apoptosis. It recruits HDAC1 and binds to methyl-CpG. UHRF2 also participates in the maturation of Hepatitis B virus (HBV) through interacting with HBV core protein and promoting its degradation. UHRF2 contains an N-terminal ubiquitin-like domain (UBL), a tandem Tudor domain (TTD), a plant homeodomain (PHD) domain, a SET- and RING-associated (SRA) domain, and a C-terminal RING finger domain. The model corresponds to the first Tudor domain. The tandem Tudor domain directs binding of UHRF to the heterochromatin mark histone H3K9me3.