The Epigenomic Features and Potential Functions of PEG- and PDS-Favorable DNA G-Quadruplexes in Rice

A G-quadruplex (G4) is a typical non-B DNA structure and involved in various DNA-templated events in eukaryotic genomes. PEG and PDS chemicals have been widely applied for promoting the folding of in vivo or in vitro G4s. However, how PEG and PDS preferentially affect a subset of G4 formation genome-wide is still largely unknown. We here conducted a BG4-based IP-seq in vitro under K +PEG or K +PDS conditions in the rice genome. We found that PEG-favored IP-G4s have distinct sequence features, distinct genomic distributions and distinct associations with TEGs, non-TEGs and subtypes of TEs compared to PDS-favored ones. Strikingly, PEG-specific IP-G4s are associated with euchromatin with less enrichment levels of DNA methylation but with more enriched active histone marks, while PDS-specific IP-G4s are associated with heterochromatin with higher enrichment levels of DNA methylation and repressive marks. Moreover, we found that genes with PEG-specific IP-G4s are more expressed than those with PDS-specific IP-G4s , suggesting that PEG/PDS-specific IP-G4s alone or coordinating with epigenetic marks are involved in the regulation of the differential expression of related genes, therefore functioning in distinct biological processes. Thus, our study provides new insights into differential impacts of PEG and PDS on G4 formation, thereby advancing our understanding of G4 biology.