The genetic fine structure of nonsense suppressors in Schizosaccharomyces pombe

Abstract

Meiotic and mitotic fine-structure maps of two efficient UGA suppressors of Schizosaccharomyces pombe which are known (sup3-e) or inferred (sup9-e) to code for two serine tRNAs carrying the mutant anticodon U*CA (Kohli et al. 1979a, b, Rafalski et al. 1979) are presented. Maps based on spontaneous meiotic, spontaneous mitotic and MMS induced mitotic recombination between the primary site of the anticodon mutation and a number of inactivating second-site mutations are similar. Specific marker effects, which drastically increase the frequency of spontaneous meiotic and mitotic recombination in crosses involving one or the other of four exceptional sites (including the anticodon sites of both sup3-e and sup9-e), disappear when mapping is based on MMS induced mitotic recombination. The meiotic marker effect characterizing the anticodon site of one of the two efficient UGA suppressors (sup3-e) also disappears upon further mutation to an inefficient UAA suppressor allele (sup3-i), as shown by its absence in a fine-structure map based on meiotic recombination between the anticodon mutation of this ochre suppressor allele and a new set of inactivating second-site mutations derived from it.

The Meiotic Recombination Hot Spot ura4A in Schizosaccharomyces pombe

“…The ura4A allele entering the cross with the h ϩ parent acts as information acceptor 1970; Fujitani and Kobayashi 1997). The extreme map expansion found in S. pombe tRNA genes (Fincham and almost twice as often as the allele being contributed by the h Ϫ parent (167: 94, Q ϭ 0.56), as seen by summing Holliday 1970) was later attributed to marker effects of G-to-C transversion mutations (Hofer et al 1979; Schär up of the tetrad analysis of all mutants (Table 2). In the random spore analysis of two-factor crosses (Table and Kohli 1993).…”

Substrate recognition and identification of splice sites by the tRNA-splicing endonuclease and ligase from Saccharomyces cerevisiae.

“…Finally, we suggest that splice sites may be determined largely through their position relative to sites within the tRNA-like domain of the precursors. Several of these important sites were identified, and others are proposed based on the data described here.The sup3-e and sup9-e loci in Schizosaccharomyces pombe encode efficient serine-inserting UGA suppressors (11,12,33). The dimeric transcripts of these two loci contain tRNAser and tRNAMet sequences joined by a sevennucleotide spacer.…”

“…The sup3-e and sup9-e loci in Schizosaccharomyces pombe encode efficient serine-inserting UGA suppressors (11,12,33). The dimeric transcripts of these two loci contain tRNAser and tRNAMet sequences joined by a sevennucleotide spacer.…”

“…tRNA gene mutations. The isolation and characterization of suppressor-inactive mutants of sup3-e and sup9-e has been described previously (11,21,33 …”

“…A number of years ago, Hofer et al (11) isolated S. pombe strains in which nonsense suppression by sup3-e or sup9-e tRNA was abolished as a result of mutations at the suppressor locus. Subsequently, the genes encoding the nonsense suppressors and a number of the suppressor-inactive derivatives were isolated and characterized (12,21,33).…”