A New Recombinational DNA Repair Gene From Schizosaccharomyces pombe With Homology to Escherichia coli RecA

Abstract

A new DNA repair gene from Schizosaccharomyces pombe with homology to RecA was identified and characterized. Comparative analysis showed highest similarity to Saccharomyces cerevisiae Rad55p. rhp55+ (rad homologue pombe 55) encodes a predicted 350-amino-acid protein with an Mr of 38,000. The rhp55Δ mutant was highly sensitive to methyl methanesulfonate (MMS), ionizing radiation (IR), and, to a lesser degree, UV. These phenotypes were enhanced at low temperatures, similar to deletions in the S. cerevisiae RAD55 and RAD57 genes. Many rhp55Δ cells were elongated with aberrant nuclei and an increased DNA content. The rhp55 mutant showed minor deficiencies in meiotic intra- and intergenic recombination. Sporulation efficiency and spore viability were significantly reduced. Double-mutant analysis showed that rhp55+ acts in one DNA repair pathway with rhp51+ and rhp54+, homologs of the budding yeast RAD51 and RAD54 genes, respectively. However, rhp55+ is in a different epistasis group for repair of UV-, MMS-, or γ-ray-induced DNA damage than is rad22+, a putative RAD52 homolog of fission yeast. The structural and functional similarity suggests that rhp55+ is a homolog of the S. cerevisiae RAD55 gene and we propose that the functional diversification of RecA-like genes in budding yeast is evolutionarily conserved.

The involvement of Srs2 in post-replication repair and homologous recombination in fission yeast

“…In the absence of the homologues of these proteins in S.pombe (Rhp55 and Rhp57, respectively) Rhp51-dependent recombination is ablated (our unpublished data). However, a rhp51D mutant is more sensitive to DNA damaging agents than either rhp55D or rhp57D mutants, which indicates that Rhp51 can still promote repair/tolerance in the absence of Rhp55±Rhp57 (32,33). Based on this we wondered whether deleting srs2 would improve the stability of the Rhp51 nucleoprotein ®lament in the absence of Rhp55±Rhp57 enabling it to more ef®ciently promote DNA repair.…”

A RecA Homologue in Ustilago maydis That Is Distinct and Evolutionarily Distant from Rad51 Actively Promotes DNA Pairing Reactions in the Absence of Auxiliary Factors

“…Genetic analysis supports the notion that Rad55 and Rad57 are not essential for strand exchange since overexpression of RAD51 can suppress the DNA repair deficiency of rad55 or rad57 mutants ( , ). A similar mechanism may be operational in S. pombe where genes orthologous to RAD55 and RAD57 are present and the DNA repair deficiency in an rhp57 mutant can be partially suppressed by increasing the copy number of rhp51 + encoding the Rad51 ortholog ( , ). But in U. maydis , the relationship between Rad51 and Rec2 appears to be different ().…”