Miao-Chih Tsai

A Lot of HOTAIR The roles of several classes of small (<50 nucleotides) noncoding RNAs are beginning to be defined in molecular detail, whereas the function of most of the long (∼200+ nucleotides), intergenic noncoding (linc)RNAs found in most eukaryotic genomes remains something of a mystery. The HOTAIR lincRNA, which is transcribed from the mouse HOXC locus, binds to the Polycomb Repressive Complex 2 (PRC2) and recruits it to HOXD and other genes, where its histone methylase activity acts to repress gene transcription. Tsai et al. (p. 689 , published online 8 July) now show that HOTAIR also binds to a histone demethylase enzyme, LSD1, part of the CoREST/REST repressor complex. LSD1 acts to remove transcription-activating histone marks, reinforcing the repressive activity of the PRC2 complex. HOTAIR thus functions as a platform for the coordinated binding of PRC2 and LSD1-containing complexes to genes, as revealed in a genome-wide analysis of PRC1/CoREST/REST co-regulated genes.

The process of cancer metastasis involves a series of sequential and complex steps. Here we give a perspective on recent results regarding noncoding transcription in cancer progression, focusing on the emerging role of long intergenic noncoding RNAs (lincRNAs). LincRNAs target chromatin modification complexes or RNA-binding proteins to alter gene expression programs. Similarly to miRNAs, lincRNAs exhibit distinct gene expression patterns in primary tumors and metastases. We discuss how lincRNAs can be used for cancer diagnosis and prognosis and serve as potential therapeutic targets.