Fig. 1

Genomic context and mechanisms of action of lncRNAs. a LncRNAs can be categorized according to their genomic loci relative to protein-coding genes. Intergenic lncRNAs (lincRNAs) are separate transcription units from protein-coding genes. Among them, a class may be transcribed from enhancers (eRNAs). Intronic lncRNAs are generated from the introns of protein-coding genes without overlapping with exons. Antisense lncRNAs are transcribed in opposite direction of protein-coding genes and overlap with the exons. Divergent lncRNAs are normally initiated from the promoter region of protein-coding genes. b LncRNAs exploit distinct mechanisms to elicit their regulatory roles in gene expression. ① lncRNAs can recruit proteins such as chromatin modifiers to target DNA; ② lncRNAs may act as decoy to titrate away DNA binding proteins like transcription factors; ③ lncRNAs can function as scaffold to bring multiple proteins into a complex; ④ to organize higher-order nuclear structure; ⑤ eRNAs can interact with Mediator and/or Cohesin complex to mediate and/or stabilize chromosomal looping between enhancers and cognate promoters. In cytoplasm, ⑥ lncRNAs can influence translation through intervening the loading of polysomes to mRNAs; ⑦ lncRNAs can serve as miRNA sponges to release their inhibitory roles on target mRNAs; ⑧ lncRNAs can regulate mRNA decay pathway, stabilizing or destabilizing mRNAs through RNA/RNA interaction with mRNA