Identification of Genes Required for Minisatellite Instability

Abstract

Rare alleles of minisatellites, repetitive DNA tracts whose repeat units range from 15 to 100 base pairs in length, have been correlated with human diseases including breast, colon, and urinary cancer. Little is known about the regulation of minisatellite stability. The Kirkpatrick lab conducted a color-based screen that identified factors involved in minisatellite stability during stationary phase using the yeast Saccharomyces cerevisiae. Factors were identified by screening for mutants that destabilized a minisatellite repeat construct in the coding region of the ADE2 gene. One of the factors identified in this screen was the zinc transporter gene ZRT1. I followed up these findings by identifying and sequencing mutations that suppressed the minisatellite instability phenotype in the ZRT1 null strains. To identify a suppressor gene, I transformed a yeast genomic plasmid library into a suppressor mutant stain, selected transformants that reverted to the parental phenotype, then rescued the candidate plasmids and sequenced them. I also identified specific mutations in the suppressor genes PET112 and IFM1 by amplification and sequencing. Both of these genes are involved in mitochondrial function. This suppressor screen has shown that many processes are involved in minisatellite stability during stationary phase. Further investigation is needed to identify other genes involved in the ZRT1 pathway, and to determine how these genes affect minisatellite stability. Understanding the regulation of minisatellite stability in yeast could lead to effective treatment and prevention for many human diseases.