An RNA matchmaker protein regulates the activity of the long noncoding RNA HOTAIR.

The human long noncoding RNA (lncRNA) HOTAIR acts in trans to recruit the Polycomb repressive complex 2 (PRC2) to the HOXD gene cluster and to promote gene silencing during development. In breast cancers, overexpression of HOTAIR increases metastatic potential via the repression of many additional genes. It has remained unclear what factors determine HOTAIR-dependent PRC2 activity at specific genomic loci, particularly when high levels of HOTAIR result in aberrant gene silencing. To identify additional proteins that contribute to the specific action of HOTAIR, we performed a quantitative proteomic analysis of the HOTAIR interactome. We found that the most specific interaction was between HOTAIR and the heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1, a member of a family of proteins involved in nascent mRNA processing and RNA matchmaking. Our data suggest that A2/B1 are key contributors to HOTAIR-mediated chromatin regulation in breast cancer cells: A2/B1 knockdown reduces HOTAIR-dependent breast cancer cell invasion and decreases PRC2 activity at the majority of HOTAIR-dependent loci. We found that the B1 isoform, which differs from A2 by 12 additional amino acids, binds with highest specificity to HOTAIR. B1 also binds chromatin and associates preferentially with RNA transcripts of HOTAIR gene targets. We furthermore demonstrate a direct RNA-RNA interaction between HOTAIR and a target transcript that is enhanced by B1 binding. Together, these results suggest a model in which B1 matches HOTAIR with transcripts of target genes on chromatin, leading to repression by PRC2.

Chemoenzymatic synthesis of trehalose analogues: rapid access to chemical probes for investigating mycobacteria.

Trehalose analogues are emerging as valuable tools for investigating Mycobacterium tuberculosis, but progress in this area is slow due to the difficulty in synthesizing these compounds. Here, we report a chemoenzymatic synthesis of trehalose analogues that employs the heat-stable enzyme trehalose synthase (TreT) from the hyperthermophile Thermoproteus tenax. By using TreT, various trehalose analogues were prepared quickly (1 h) in high yield (up to >99 % by HPLC) in a single step from readily available glucose analogues. To demonstrate the utility of this method in mycobacteria research, we performed a simple "one-pot metabolic labeling" experiment that accomplished probe synthesis, metabolic labeling, and imaging of M. smegmatis in a single day with only TreT and commercially available materials.