Molecular functions and biological roles of long non-coding RNAs in human physiology and disease.

The human genome has been demonstrated to be pervasively transcribed, with a large fraction of the transcriptome representing non-protein-coding RNA species. A relatively novel class of non-coding RNAs, referred to as long non-coding RNAs (lncRNAs), has attracted increasing attention over recent years. Long non-coding RNAs comprise a very heterogenous class of transcripts that exert various functions in mammalian cells. Although the number of identified and annotated lncRNAs has been increasing steadily, our understanding of the biological roles for the vast majority of these transcripts remains limited. In this review, a broad concept of the currently known lncRNA modes of action is provided. Examples of mammalian lncRNAs with well-established biological roles are highlighted and their molecular functions and mechanisms are discussed in detail.