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DNA:RNA hybrid formation is emerging as a significant cause of genome instability in biological systems ranging from bacteria to mammals. Here we describe the genome-wide distribution of DNA:RNA hybrid prone loci in Saccharomyces cerevisiae by DNA:RNA immunoprecipitation (DRIP) followed by hybridization on tiling microarray. These profiles show that DNA:RNA hybrids preferentially accumulated at rDNA, Ty1 and Ty2 transposons, telomeric repeat regions and a subset of open reading frames (ORFs). The latter are generally highly transcribed and have high GC content. Interestingly, significant DNA:RNA hybrid enrichment was also detected at genes associated with antisense transcripts. The expression of antisense-associated genes was also significantly altered upon overexpression of RNase H, which degrades the RNA in hybrids. Finally, we uncover mutant-specific differences in the DRIP profiles of a Sen1 helicase mutant, RNase H deletion mutant and Hpr1 THO complex mutant compared to wild type, suggesting different roles for these proteins in DNA:RNA hybrid biology. Our profiles of DNA:RNA hybrid prone loci provide a resource for understanding the properties of hybrid-forming regions in vivo, extend our knowledge of hybrid-mitigating enzymes, and contribute to models of antisense-mediated gene regulation. A summary of this paper was presented at the 26th International Conference on Yeast Genetics and Molecular Biology, August 2013., Author Summary RNA processing factors are mutated in human cancers, inherited developmental disorders and neurodegenerative syndromes. Defects in RNA processing have been associated with increased levels of mutations and DNA damage in part via the formation of DNA:RNA hybrids. Although it is likely that specific regions of the genome are more prone to DNA:RNA hybrid formation, a map of hybrid-prone regions is not available. In this study, we describe the genome-wide distribution of DNA:RNA hybrids in both normal and mutant Saccharomyces cerevisiae cells. The resulting profiles contribute to both our understanding of the general properties of hybrid-forming loci and to our knowledge of hybrid-mitigating enzymes. Interestingly, significant DNA:RNA hybrid enrichment was detected at genes associated with antisense transcription. We show that overexpression of RNase H, which degrades the RNA in hybrids, significantly affects the expression of genes associated with antisense transcripts. These findings support a role for DNA:RNA hybrids in regulation of gene expression by antisense transcripts.