[HOK], a new yeast non-Mendelian trait, enables a replication-defective killer plasmid to be maintained

Genetics. 1982 Feb;100(2):159-74. doi: 10.1093/genetics/100.2.159.

Abstract

The K1 killer plasmid, [KIL-k1], of Saccharomyces cerevisiae is a 1.25 x 10(6) dalton linear double-stranded RNA plasmid coding for a protein toxin and immunity to that toxin. The [KIL-sd1] plasmid is a replication-defective mutant of [KIL-k1] that depends on one of the recessive chromosomal superkiller (ski-) mutations for its maintenance (Toh-e and Wickner 1979). This report concerns a means by which [KIL-sd1] can be stably maintained in a SKI+ host. Strains carrying a plasmid we call [HOK] (helper of killer) stably maintain [KIL-sd1]. [HOK] segregates 4 [HOK]:0 in meiotic crosses and is efficiently transferred by cytoplasmic mixing (heterokaryon formation). [HOK] depends for its maintenance on the products of PET18, MAK3, and MAK10, three chromosomal genes needed to maintain [KIL-k1], but is independent of 10 other MAK genes and of MKT1. [HOK] is not mitochondrial DNA and is unaffected by agents which convert psi+ strains to psi-. [HOK] is also distinct from the previously described plasmids [URE3], 20S RNA, 2 mu DNA, and [EXL]. Strains lacking [HOK] consistently have a four-fold lower copy number of L double-stranded RNA than strains carrying [HOK].

Publication types

  • Comparative Study

MeSH terms

  • Crosses, Genetic
  • Genes*
  • Genotype
  • Mutation*
  • Phenotype
  • Plasmids*
  • RNA, Double-Stranded / genetics
  • RNA, Fungal / genetics*
  • Saccharomyces cerevisiae / genetics*
  • Species Specificity

Substances

  • RNA, Double-Stranded
  • RNA, Fungal