RING finger, H2 subclass, found in p53-induced RING-H2 protein (Pirh2) and similar proteins
Pirh2, also known as RING finger and CHY zinc finger domain-containing protein 1 (Rchy1), androgen receptor N-terminal-interacting protein, CH-rich-interacting match with PLAG1, RING finger protein 199 (RNF199), or zinc finger protein 363 (ZNF363), is a p53 inducible E3 ubiquitin-protein ligase that functions as a negative regulator of p53. It preferably ubiquitylates the tetrameric form of p53 in vitro and in vivo, suggesting a role of Pirh2 in downregulating the transcriptionally active form of p53 in the cell. Moreover, Pirh2 inhibits the transcriptional activity of p73, a homolog of the tumor suppressor p53, by promoting its ubiquitination. It also monoubiquitinates DNA polymerase eta (PolH) to suppress translesion DNA synthesis. Furthermore, Pirh2 functions as a negative regulator of the cyclin-dependent kinase inhibitor p27(Kip1) function by promoting ubiquitin-dependent proteasomal degradation. Pirh2 enhances androgen receptor (AR) signaling through inhibition of histone deacetylase 1 (HDAC1) and is overexpressed in prostate cancer. It interacts with TIP60 and this association may regulate Pirh2 stability. In addition, the oncoprotein pleomorphic adenoma gene like 2 (PLAGL2) can bind to the Pirh2 dimer and therefore control the stability of Pirh2. Pirh2 contains a total of nine zinc-binding sites with six located at the N-terminal region, two in the C3H2C3-type RING-H2 domain, and one in the C-terminal region. Nine zinc binding sites comprise three different zinc coordination schemes, including RING type cross-brace zinc coordination, C4 zinc finger, and a novel left-handed beta-spiral zinc-binding motif formed by three recurrent CCHC sequence motifs. This subfamily also includes Drosophila melanogaster Deltex, a ubiquitously expressed cytoplasmic ubiquitin E3 ligase that mediates Notch activation in Drosophila. It selectively suppresses T-cell activation through degradation of a key signaling molecule, MAP kinase kinase kinase 1 (MEKK1). It also inhibits Jun-mediated transcription at the stage of Ras-dependent Jun N-terminal protein kinase (JNK) activation. Deltex contains N-terminal two Notch-binding WWE domains that physically interact with the Notch ankyrin domains, a proline-rich motif that shares homology with SH3-binding domains, and a RING finger at the C-terminus.
Comment:C3H2C3-type RING-H2 finger consensus motif: C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-H-X2-C-X(4-48)-C-X2-C, where X is any amino acid and the number of X residues varies in different fingers
Comment:A RING finger typically binds two zinc atoms, with its Cys and/or His side chains in a unique "cross-brace" arrangement.
Jiyao W et al.(2023). "The conserved domain database in 2023.",