9407612 Abstract The major goals of this project are to increase the general utility of insertional mutagenesis using inducible Ty elements in the budding yeast Saccharomyces cerevisiae, and to gain a better understanding of the mechanism of gene disruption by Ty. In addition, the techniques used are designed insofar as possible to involve undergraduate students, to increase their understanding of and interest in scientific research. This study uses a plasmid- borne Ty element controlled by an inducible promoter, GAL1, and marked with the HIS3 gene. Disruptions of essential genes on several chromosomes have been isolated by inducing transposition in a diploid strain and screening for cases in which the TyHis+ haploid progeny is non-viable. The predicted rate for lethal gene disruptions, if the pattern of insertions is random, is about 12% of TyHis+ insertions. The observed rate is 0.3%, indicating a limited number of permissible targets. Attempts to broaden the target region for Ty insertion will include use of mutant strains with altered chromosome function, and transposition induction in meiotic cells. An alternate screening technique, to isolate mutants resistant to alpha-mating-type pheromone, produced insertionsof TyHis+ multimers into HML alpha, a normally silent gene containinginformation for mating-type control. Unlinked suppressors which restore silencing in hml alpha ::TyHIS3 mutants have been isolated as well. Characterization of the suppressors, including their interactions with genes affecting chromatin structure, will increase understanding of the silencing mechanism at HML alpha and may help to define some properties of this particular target of Ty integration. %%% Genetic research has given society much of the scientific knowledge from which society has so profoundly benefited. The production of mutations is an essential element of genetic research. In this project, the investigator will attempt to broaden the usefulness of a biologic al tool, the Ty element of yeast, in generating new mutations. She will also study its mechanisms of gene disruption. The investigator, a professor at a rural community college, will involve her students in this research, thus significantly raising their scientific literacy and possibly inspiring some to pursue research careers. ***
