Variant RING finger, HC subclass (C4C4-type), found in Ret finger protein-like (RFPL) family
RFPL family, also known as RING-B30 family, represents a group of RFPL gene products, RFPL1, RFPL2, RFPL3, and RFPL4A, which are characterized by containing an N-terminal RFPL1, 2, 3-specifying helix (RSH), a C4C4- or a modified C4C4-type RING finger, whose overall folding is similar to that of the typical C3HC4-type RING-HC finger, an RFPL-defining motif (RDM), and C-terminal PRY/SPRY-forming B30.2 domain. RFPL1, also known as RING finger protein 78 (RNF78), is expressed during cell differentiation, its impact on cell-cycle lengthening therefore provides novel insights into primate-specific development. RFPL2, also known as RING finger protein 79 (RNF79), shows high sequence similarity with other RFPL gene products. Its biological role remains unclear. RFPL3 interacts directly with CREB binding protein (CBP) in the nucleus of lung cancer cells. RFPL3 and CBP synergistically upregulate TERT activity and promote lung cancer growth. Moreover, RFPL3 acts as a novel E3 ubiquitin ligase modulating the integration activity of human immunodeficiency virus, type 1 (HIV-1) preintegration complex. RFPL4A, also known as RING finger protein 210 (RNF210), is a novel factor that increases the G1 population and decreases sensitivity to chemotherapy in human colorectal cancer cells. This family corresponds to the C4C4-type RING finger. RFPL4A lacks the fourth conserved zinc-binding residue, cysteine, and the eighth zinc-binding residue, cysteine, in RFPL2 is replaced by serine.