Molecular cloning of ring finger protein 21 (RNF21)/interferon-responsive finger protein (ifp1), which possesses two RING-B box-coiled coil domains in tandem

We have cloned the full length of a novel cDNA, named ring finger protein 2 1 (RNF21), composed of the RING finger-B box-coiled coil (RBCC) domain and the B30.2 domain, which are characteristic of the RBCC-B30.2 family, As a s tructural feature, the RNF21 cDNA possessed at least three kinds of isoform s, due to alternative splicing, consisting of the long form with the RBCC-R BCC-B30.2 domain, the medium form with the RBCC-B30.2 domain, and the short form with only the RBCC domain. Moreover, respective transcripts correspon ding to the three isoforms were detected in various human organs by reverse transcription-PCR and Northern blot analyses. Interestingly, the medium fo rm of the RNF21 mRNA expressed most predominantly was dramatically up-regul ated within 8-16 h by interferon stimulation of HeLa cells. These findings suggest that RNF21 is a downstream gene that may mediate interferon's biolo gical action. (C) 2000 Academic Press.