RNA:DNA hybrids in the human genome have distinctive nucleotide characteristics, chromatin composition, and transcriptional relationships (RNA-seq). Homo sapiens

Mapping of RNA:DNA hybrids in human cells reveals a number of characteristics of these non-canonical nucleic acid structures. A directional sequencing approach reveals the RNA component of the RNA:DNA hybrid to be purine-rich, indicating a thermodynamic contribution to the stability of these structures. The RNA:DNA hybrids are enriched at loci with decreased DNA methylation and increased DNase hypersensitivity, and within larger domains with characteristics of heterochromatin formation. Studies of chromatin at RNA:DNA hybrids shows the presence of the ILF2 and ILF3 transcription factors, supporting a model of certain transcription factors binding preferentially to the RNA:DNA conformation. Overall, there is little to indicate a dependence for RNA:DNA hybrids forming co-transcriptionally, with results from the ribosomal DNA repeat unit instead supporting a model of RNA generating these structures in trans. The results of the study indicate heterogeneous functions of these genomic elements and new insights into their formation and stability in vivo. Overall design: Investigation of expression data genome-wide in HEK293T and IMR-90 cells through RNA-seq, including rRNA