Mechanisms of lncRNA biogenesis as revealed by nascent transcriptomics

Mammalian genomes express two principal gene categories through RNA polymerase II-mediated transcription: protein-coding transcription units and non-coding RNA transcription units. Non-coding RNAs are further divided into relatively abundant structural RNAs, such as small nuclear RNAs, and into a myriad of long non-coding RNAs (lncRNAs) of often low abundance and low stability. Although at least some lncRNA synthesis may reflect transcriptional 'noise', recent studies define unique functions for either specific lncRNAs or for the process of lncRNA synthesis. Notably, the transcription, processing and metabolism of lncRNAs are regulated differently from protein-coding genes. In this Review, we provide insight into the regulation of lncRNA transcription and processing gleaned from the application of recently devised nascent transcriptomics technology. We first compare and contrast different methodologies for studying nascent transcription. We then discuss the molecular mechanisms regulating lncRNA transcription, especially transcription initiation and termination, which emphasize fundamental differences in their expression as compared with protein-coding genes. When perturbed, lncRNA misregulation leads to genomic stress such as transcription-replication conflict and R-loop-mediated DNA damage. We discuss many unresolved but important questions about the synthesis and potential functions of lncRNAs. Mammalian RNA polymerase II transcribes protein-coding genes and non-coding transcription units, including long non-coding RNAs (lncRNAs). Studies applying recently developed nascent transcriptomics technology have revealed differences in transcription initiation and termination between lncRNAs and protein-coding genes, bearing relevance to genomic stress and DNA damage.

Automated summary

Mammalian genomes express protein-coding and non-coding RNA genes. Recent studies have revealed differences in transcription initiation and termination between non-coding RNA genes and protein-coding genes, which are relevant to genomic stress and DNA damage.