Time-Dependent Nucleosome Remodeling During Galactose-Induced Ty1 Expression in Saccharomyces cerevisiae

We find that changes in carbon source do not substantially alter genome-wide nucleosome organization. In contrast, galactose induction of Ty1 expression revealed time-dependent changes in nucleosome occupancy. Nucleosome organization is unchanged across pre-induction, 6-hour galactose exposure, and post-induction repressing conditions, but nucleosome occupancy shifted at 12 and 24 hours, with changes evident at both Pol II and tRNA genes.

We also found that Ty1 integration events are rare at early time points, emerge by 12 hours, and accumulate substantially by 24 hours. Ty1 preferentially targets nucleosomal DNA, but prolonged induction shifts insertion positions relative to nucleosomes. We also find that Ty1 preferentially targets nucleosomal DNA that lies in close proximity to histones, with this preference showing time-dependent shifts during induction.