Ring Finger Protein 187 (RNF187)

RACO1, as a JUN-interacting protein. The deduced 235-amino acid protein, which is translated from a nonconventional CTG initiation codon, has a calculated molecular mass of 26 kD. It contains an N-terminal C4HC3 RING domain. Western blot analysis detected RACO1 expression in human HeLa and HCT116 cells and in rat PC12 cells. In transfected HEK293 cells, RACO1 localized predominantly to cytoplasm, with some RACO1 localized to nuclei.

Coexpression of RACO1 elevated JUN-dependent activation of a reporter gene. A constitutively active form of MEKK1 (MAP3K1) enhanced JUN coactivation by RACO1, whereas inhibition of MEK1 (MAP2K1) and MEK2 (MAP2K2) reduced JUN coactivation by RACO1.