Yawei Gao

A new layer of transcriptional control N 6 -methyladenosine (m 6 A) is the most abundant messenger RNA modification in almost all eukaryotes. Liu et al. now show that m 6 A is also cotranscriptionally added onto various chromosome-associated regulatory RNAs (carRNAs) in mammalian cells. Disruption of m 6 A modification of these RNAs increases their abundance and promotes gene transcription by increasing the chromatin accessibility. Thus, m 6 A serves as a switch to regulate carRNA levels by tuning nearby chromatin state and downstream transcription. Science , this issue p. 580

N 6 -methyladenosine (m 6 A) is the most abundant internal modification on mammalian messenger RNA. It is installed by a writer complex and can be reversed by erasers such as the fat mass and obesity-associated protein FTO. Despite extensive research, the primary physiological substrates of FTO in mammalian tissues and development remain elusive. Here, we show that FTO mediates m 6 A demethylation of long-interspersed element-1 (LINE1) RNA in mouse embryonic stem cells (mESCs), regulating LINE1 RNA abundance and the local chromatin state, which in turn modulates the transcription of LINE1-containing genes. FTO-mediated LINE1 RNA m 6 A demethylation also plays regulatory roles in shaping chromatin state and gene expression during mouse oocyte and embryonic development. Our results suggest broad effects of LINE1 RNA m 6 A demethylation by FTO in mammals.