[In vivo functions of long non-coding RNAs].

Advances in genomics and molecular biology have led to discovery of a large group of previous uncharacterized long non-noncoding RNAs (lncRNAs). Whether all of these transcripts are functional remains to be elucidated, but emerging evidence indicates that many lncRNAs play roles in multiple biological processes and that dysregulation of lncRNAs is often associated with diseases. Of significant interest, recent studies suggest that almost all of the regulatory lncRNAs function through interacting with different biological macromolecules such as DNA, RNA, and protein. In this review, we summarize the mechanisms by which lncRNAs regulate gene expression at epigenetic, transcriptional and post-transcriptional levels, and discuss the role of lncRNAs in tumorigenesis and host defense. Distinct from small ncRNAs that regulate gene expression mainly through base pairing to target transcripts, most identified lncRNAs function by regu-lating protein activity or maintaining the integrity of protein complexes. As a result, identification and characterization of the lncRNA-protein interactions may be the primary task to decode functional lncRNAs.