The FAR domain defines a new Xenopus laevis zinc finger protein subfamily with specific RNA homopolymer binding activity

Abstract

The zinc finger motif defines a large superfamily of nucleic acid binding proteins. Conserved amino acid sequence elements associated with structurally variant zinc finger clusters define subfamilies of zinc finger proteins (ZFPs). The FAR domain (Finger Associated Repeats) is a novel type of repeat element found at the amino-terminus in a subfamily of Xenopus laevis ZFPs. Northern blot analyses of three different members of the FAR subfamily (XFO 6, XFO 9-3 and XFG 68) revealed that each of these genes is transcribed during oogenesis, embryogenesis and in all investigated tissues of adult animals thereby indicating a ubiquitous distribution of transcripts. All FAR-ZFPs tested so far have specific RNA homopolymer binding activity; they associate preferentially with poly(U). The FAR repeats possess limited primary sequence homology with a sequence in the nucleolar shuttling protein NO38, within a region that contains a casein kinase II phosphorylation site.