Transcriptional interference by small transcripts in proximal promoter regions

Abstract

Proximal promoter regions (PPR) are heavily transcribed yielding different types of small RNAs. The act of transcription within PPRsmight regulate downstream gene expression via transcriptional interference (TI). For analysis, we investigated capped and polyadenylated small RNA transcripts within PPRs of human RefSeq genes in eight different cell lines. Transcripts of our datasets overlapped with experimentally determined transcription factor binding sites (TFBS). For TFBSs intersected by these small RNA transcripts, we established negative correlation of sRNA expression levels and transcription factor (TF) DNA binding affinities; suggesting that the transcripts acted via TI. Accordingly, datasets were designated as TFbiTrs (TF-binding interfering transcripts). Expression of most TFbiTrs was restricted to certain cell lines. This facilitated the analysis of effects related to TFbiTr expression for the same Ref-Seq genes across cell lines. We consistently uncovered higher relative TF/DNA binding affinities and concomitantly higher expression levels for RefSeq genes in the absence of TFbiTrs. Analysis of corresponding chromatin landscapes supported these results. ChIA-PET revealed the participation of distal enhancers in TFbiTr transcription. Enhancers regulating TFbiTrs, in effect, act as repressors for corresponding downstream RefSeq genes. We demonstrate the significant impact of TI on gene expression using selected small RNA datasets.