MSG1 AND ITS RELATED PROTEIN MRG1 SHARE A TRANSCRIPTION ACTIVATING DOMAIN

MSG1 is a recently described melanocyte-specific nuclear protein whose biochemical function is unknown [Shioda et al. (1996) Proc. Natl. Aca d. Sci. USA 93, 12298-12303]. Two human cDNA sequences found in the ES T (expressed sequence tag) database were predicted to encode a small p eptide (45 aa) that showed 69% identity to the C-terminal sequence of MSG1, suggesting the existence of a novel MSG1-related protein. Based on these EST sequences, we isolated a novel gene, MRG1 (MSG1-Related G ene 1), by the 5'-RACE (rapid amplification of cDNA ends) technique. T he MRG1 mRNA transcript is expressed widely and encodes a nuclear prot ein that share two highly conserved domains, CR1 (14 aa) and CR2 (appr ox. 50 aa), with MSG1. The CR2 domain is significantly acidic and acti vates transcription in yeast cells. The full-length MSG1 and MRG1 fuse d to GAL4 DNA-binding domain activates transcription in mammalian cell s, and this is dependent on the presence of the CR2 domain. These resu lts suggest that MRG1 and MSG1 may function as transcription activator s. (C) 1997 Elsevier Science B.V.