Genes with internal repeats require the THO complex for transcription

Abstract

A genome-wide screen for promoter-independent regulators of the Saccharomyces cerevisiae adhesin FLOII identified 37 novel regulators. Among the mutants with the strongest phenotype were the deletions of genes encoding subunits of the evolutionarily conserved THO complex. The THO complex, which is recruited to actively transcribed genes, is required for the efficient expression of FLO I and other yeast genes that have long internal tandem repeats. FLO I transcription elongation in Tho- mutants is hindered in the region of the tandem repeats, resulting in a loss of function. Moreover, the repeats become genetically unstable in Tho- mutants. A FLO I gene without the tandem repeats is transcribed equally well in Tho+ or Tho- strains. The Tho- defect in transcription is suppressed by overexpression of topoisomerase I, suggesting that the THO complex functions to rectify aberrant structures that arise during transcription.