Unexpected functions of lncRNAs in gene regulation.

Long non-coding RNAs (lncRNAs) are a group of molecules that function in gene regulation in yeast, plants and mammals. The precise mechanisms of action for lncRNAs, however, remain largely unclear. The GAL gene cluster has been used as a model system to study the function of these molecules in Saccharomyces cerevisiae, with a historical focus on lncRNA-dependent repression. Strikingly, in characterizing the role of the RNA helicase Dbp2, we discovered that the GAL lncRNAs could also promote transcriptional activation of the targeted GAL protein-coding genes. Interestingly, these lncRNAs help determine how quickly the GAL genes can be induced in response to galactose, without altering final steady-state transcript levels. This unexpected finding suggests that one role for lncRNAs is to promote the timing of gene expression. Herein, we discuss our discoveries in the context of current models of lncRNA functions in eukaryotes, with a key emphasis on future challenges for genomic research.