Gene structure and alternative splicing of XFG 5-1, a X. laevis Zn finger protein with RNA homopolymer binding activity.

We describe the fine-structure of the Xenopus laevis XFG 5-1 gene which codes for an RNA homopolymer binding Zn finger protein of the FAR (Finger Associated Repeat) subfamily. The gene contains six exons, i.e., a leader exon (I), four exons (II-V), each of them encoding one individual copy of the FAR repeat, and one exon (VI) encoding the linker as well as the complete multifinger-region of the corresponding protein. Isolation and characterization of distinct cDNAs revealed that primary transcripts are alternatively spliced, thereby leading either to mRNAs containing different copy numbers of the FAR repeat or, by utilization of an alternative splice acceptor site in front of exon VI, to an extension of the linker region between the FAR repeats and the multifinger domain. We also describe the fine-structure of a closely related gene, termed XFG 5-2, which is located downstream to the XFG 5-1 gene. The general structural organization in both genes is identical, but point mutations should give rise to a XFG 5-2 protein with a different number of Zn finger units.