THE FAR DOMAIN DEFINES A NEW XENOPUS-LAEVIS ZINC-FINGER PROTEIN SUBFAMILY WITH SPECIFIC RNA HOMOPOLYMER BINDING-ACTIVITY

The zinc finger motif defines a large superfamily of nucleic acid bind ing proteins. Conserved amino acid sequence elements associated with s tructurally variant zinc finger clusters define subfamilies of zinc fi nger proteins (ZFPs). The FAR domain (Finger Associated Repeats) is a novel type of repeat element found at the amino-terminus in a subfamil y of Xenopus laevis ZFPs. Northern blot analyses of three different me mbers of the FAR subfamily (XFO 6, XFO 9-3 and XFG 68) revealed that e ach of these genes is transcribed during oogenesis, embryogenesis and in all investigated tissues of adult animals thereby indicating a ubiq uitous distribution of transcripts. All FAR-ZFPs tested so far have sp ecific RNA homopolymer binding activity; they associate preferentially with poly(U). The FAR repeats possess limited primary sequence homolo gy with a sequence in the nucleolar shuttling protein NO38, within a r egion that contains a casein kinase II phosphorylation site.