R-loop formation is a distinctive characteristic of unmethylated human CpG island promoters.

ABSTRACT: CpG islands (CGIs) function as promoters for approximately 60% of human genes. Most of these elements remain protected from CpG methylation, a prevalent epigenetic modification associated with transcriptional silencing. Here, we report that methylation-resistant CGI promoters are characterized by significant strand asymmetry in the distribution of guanines and cytosines (GC skew) immediately downstream from their transcription start sites. Using innovative genomics methodologies, we show that transcription through regions of GC skew leads to the formation of long R loop structures. Furthermore, we show that GC skew and R loop formation potential is correlated with and predictive of the unmethylated state of CGIs. Finally, we provide evidence that R loop formation protects from DNMT3B1, the

SUBMITTER: Ginno PA 

PROVIDER: S-EPMC3319272 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature