Gene activation by copy transposition in mating-type switching of a homothallic fission yeast

✍ Scribed by Richard Egel; Herbert Gutz

• Publisher: Springer-Verlag
• Year: 1981
• Tongue: English
• Weight: 759 KB
• Volume: 3
• Category: Article
• ISSN: 0172-8083
• DOI: 10.1007/bf00419574

✦ Synopsis

Mating-type switching in homothallic clones of the fission yeast, Schizosaccharomyces pombe, appears to follow the same route as previously found for "mutations" from homothallism to heterothallic strains. A copy of mat2-P is transposed to and inserted at rnatl, where it functionally replaces the rnatJ-M allele, and only the mat1 segment is expressed (!) to determine the actual mating type: marl-M(!) mat2-P = 0, ~ ® = rnatl-P(!) mat2-P. This phenomenon has hitherto been concealed by the high switch-back rate from @ to @ observed in homothallic wild-type strains. It only becomes apparent in the presence of mutant "switching genes", which retard the rates of mating-type interconversion and temporarily freeze one or the other state of gene activation at the rnatl segment. Mutations to lowered rates of switching are found to map both inside and outside the mating-type locus. While the internal mutations of this kind exert their effect autonomously in the cis-configuration, the unlinked mutations are recessive to their wildtype alleles.