Suppression in the Yeast Saccharomyces cerevisiae

INTRODUCTION It can be said that significant advancements in determining the molecular basis of suppression have been made so far only with the prokaryotes Escherichia coli and Salmonella typhimurium and with the eukaryotic yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. With notable and important exceptions, the properties of suppressors from yeast are identical or similar to the properties of suppressors from bacteria. In fact, the conceptual framework for the work on yeast suppressors has been based on the earlier and more extensive work on bacterial suppressors. In this brief review, the suppressors of the yeast S. cerevisiae are tabulated, and their properties are summarized. The chromosomal map positions of many of the suppressors can be found on the genetic map that is presented in Appendix I of this volume. Suppressors in yeast, as well as in prokaryotes, have proved to be important for probing the translational process, for investigating tRNA biosynthesis, and for providing a convenient means of deducing the nucleotide sequences of suppressible mutations. Investigations with bacteria have shown that extragenic information suppression is primarily mediated by altered tRNAs or altered ribosomes. Another class of suppressors, the polarity suppressors, has altered components required for proper transcriptional termination, and these types of suppressors are not to be expected to occur in yeast or other eukaryotes. Altered tRNAs with suppressor activity can have base changes within or outside anticodons, or they can have bases lacking proper modifications. Prokaryotic tRNA suppressors have been reviewed recently by Korner et al. (1978), Smith (1979), and...