Chemical genomic screening of a Saccharomyces cerevisiae genomewide mutant collection reveals genes required for defense against four antimicrobial peptides derived from proteins found in human saliva.

To compare the effects of four antimicrobial peptides (MUC7 12-mer, histatin 12-mer, cathelicidin KR20, and a peptide containing lactoferricin amino acids 1 to 11) on the yeast Saccharomyces cerevisiae, we employed a genomewide fitness screen of combined collections of mutants with homozygous deletions of nonessential genes and heterozygous deletions of essential genes. When an arbitrary fitness score cutoffs of 1 (indicating a fitness defect, or hypersensitivity) and -1 (indicating a fitness gain, or resistance) was used, 425 of the 5,902 mutants tested exhibited altered fitness when treated with at least one peptide. Functional analysis of the 425 strains revealed enrichment among the identified deletions in gene groups associated with the Gene Ontology (GO) terms "ribosomal subunit," "ribosome biogenesis," "protein glycosylation," "vacuolar transport," "Golgi vesicle transport," "negative regulation of transcription," and others.

Role for topoisomerase 1 in transcription-associated mutagenesis in yeast.

High levels of transcription in Saccharomyces cerevisiae are associated with increased genetic instability, which has been linked to DNA damage. Here, we describe a pGAL-CAN1 forward mutation assay for studying transcription-associated mutagenesis (TAM) in yeast. In a wild-type background with no alterations in DNA repair capacity, ≈50% of forward mutations that arise in the CAN1 gene under high-transcription conditions are deletions of 2-5 bp.