Cloning and characterization of the Schizosaccharomyces pombe homologs of the human protein Translin and the Translin-associated protein TRAX

Translin is a human octameric protein that specifically binds the single-stranded microsatellite repeats d(GT)(n) and the corresponding transcripts (GU)(n). It also binds, with lesser affinities, other single-stranded G-rich DNA and RNA sequences. TRAX is a human protein that bears a homology to Translin and interacts with it. Translin and TRAX have been proposed to be involved in DNA recombination, chromosomal translocation and mRNA transport and translation. Both proteins are highly conserved in eukaryotes, including the fission yeast Schizosaccharomyces pombe, which is amenable to genetic analysis. Here, we report the first study of the S.pombe Translin and TRAX homologs. We have deleted the genes encoding Translin and TRAX in S.pombe and found that the proliferation of the mutant cells was slightly stimulated, suggesting that these genes are not essential for the fission yeast. We have also shown that the S.pombe Translin and TRAX interact. Biochemical analysis of the S.pombe Translin, which was cloned and expressed in Escherichia coli, revealed that it is octameric and that it selectively binds d(GT)(n) and d(GTT)(n) microsatellite repeats. However, unlike the human protein, it has much higher affinities for the homologous RNA sequences (GU)(n) and (GUU)(n). These data suggest that the S.pombe Translin is primarily involved in functions related to RNA metabolism.