PROTEINS OF THE XENOPUS-LAEVIS ZINC-FINGER MULTIGENE FAMILY AS TARGETS FOR CK-II PHOSPHORYLATION

Zn finger proteins (ZFPs) of the C-2/H-2 type in Xenopus laevis are en coded by a multigene family comprising several hundred members. Based upon conserved sequence features outside the Zn finger region, ZFPs ca n be subdivided into distinct subfamilies. Two of such subfamilies are characterized by conserved, N-terminal amino acid sequences termed th e FAX and the FAR Domain. Here we present data suggesting that the zin c finger proteins of the FAR-ZFP subfamily are targets for CK II media ted phosphorylation. Expression of these proteins during oogenesis coi ncides with CK II activity in unfertilized eggs. Additionally, we have found that XlcOF 7.1, a member of the FAX-ZFP subfamily is also phosp horylated by CK II. The target sites for in vitro phosphorylation are localized within the conserved N-terminal domains but not within the Z n finger regions. However, amino acid sequence comparison revealed tha t individual phosphoacceptor sites are not generally conserved among a ll members of the respective ZFP subfamilies. The relevance of a poten tial CK II phosphorylation for the regulation of ZFP activity in vivo is discussed.