Many retrotransposons and retroviruses are thought to select integration sites through interactions with specific chromosomal proteins. In yeast, the Ty5 retrotransposon integrates preferentially within regions bound by silent chromatin, namely the telomeres and the HMR and HML mating loci. A Ty5 mutant (M3) was identified with an approximately 20-fold decrease in targeted integration as measured by a plasmid-based targeting assay. Often chromosomal insertions generated by M3, none were located at the telomeres or silent mating loci. A single amino acid change at the boundary of integrase and reverse transcriptase is responsible for the mutant phenotype. We predict that this mutation lies within a targeting domain that mediates Ty5 target choice by interacting with a component of silent chromatin.
Bibliographical noteFunding Information:
We thank members of the Voytas lab for their help and support and D. Dobbs for comments on the manuscript. This is journal paper number J-17678 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 3120 and was supported by Hatch Act and State of Iowa funds. This research was funded by grant VM-145 from the American Cancer Society.