This is the FYVE/PHD zinc finger form E3 ubiquitin-protein ligase RNF34 and RFFL, also known as Caspase regulator 1 and 2 (CARP1/2), respectively [1]. CARP2, also termed E3 ubiquitin-protein ligase rififylin (RFFL) is a novel caspase regulator that regulates the p53 signaling pathway through degrading 14-3-3 sigma and stabilizing MDM2. CARP1 ubiquitinates the caspases CASP8 and CASP10, promoting their proteasomal degradation, to negatively regulate cell death downstream of death domain receptors in the extrinsic pathway of apoptosis [2]. It negatively regulates p53/TP53 through its direct ubiquitination and targeting to proteasomal degradation [3].

1: Crystal structure of a FYVE-type zinc finger domain from the caspase regulator CARP2. Tibbetts MD, Shiozaki EN, Gu L, McDonald ER 3rd, El-Deiry WS, Shi Y; Structure. 2004;12:2257-2263. PMID:15576038

2: Suppression of caspase-8- and -10-associated RING proteins results in sensitization to death ligands and inhibition of tumor cell growth. McDonald ER 3rd, El-Deiry WS; Proc Natl Acad Sci U S A. 2004;101:6170-6175. PMID:15069192

3: CARPs are ubiquitin ligases that promote MDM2-independent p53 and phospho-p53ser20 degradation. Yang W, Rozan LM, McDonald ER 3rd, Navaraj A, Liu JJ, Matthew EM, Wang W, Dicker DT, El-Deiry WS; J Biol Chem. 2007;282:3273-3281. PMID:17121812