Researchers have been puzzled by the discovery of several-kilobase-long, polyadenylated transcripts that overlap functional coding regions but do not themselves encode proteins. A recent Nature paper by Kouji Hirota, Kunihiro Ohta, and co-workers at the RIKEN Advanced Science Institute (Japan), the University of Tokyo, and Boston College indicates that some of these ncRNAs are transcriptional trailblazers that pave the way for gene expression by remodeling promoter chromatin.
The researchers analyzed the fbp1+ locus in Schizosaccharomyces pombe, which is strongly induced by glucose starvation. Upon induction, three longer fbp1+ transcripts were sequentially detected prior to the shortest, functional transcript. These sense transcripts, which initiated upstream of the fbp1+ promoter, were polyadenylated, unspliced, and did not produce protein products. As the time of glucose starvation increased, the binding of RNA polymerase II and the opening of the chromatin configuration shifted 5’ to 3’ toward the fbp1+ promoter. The investigators proposed a model in which RNA polymerase II transcription through the fbp1+ promoter region cooperates with transcriptional activators to open the chromatin structure around the TATA box, which allows the binding of RNA polymerase II at this site and transcription of the protein-coding message. Check out all the details in Nature, October 2008