Patience is Key to RNA Pol II Relationship with Nucleosome

July 30, 2009 here’s been lots of buzz about nucleosomes and RNAs lately. In fact, just last week EpiGenie reported that transcription initiation RNAs (tiRNAs) might be formed as RNA Pol II hits a nucleosome and backtracks. Nucleosomal post-transcriptional mods can cause RNA Polymerase II to pause or abort, while others can kick transcription into high gear.
 
But Pol II’s relationship with nucleosomes remains a bit of a mystery. Why Pol II stalls, or backtracks, or proceeds is one thing. How Pol II gets past them is yet another.
 
Using a dual-trap optical tweezers system, researchers at UC-Berkeley and the NCI watched and measured as the polymerase tried to read a strand of DNA. They found that the enzyme doesn’t actively unravel DNA from the nucleosome. Rather, it waits for a stochastic hiccup to relieve the tension between the nucleosome and the DNA strand that’s wound around it, and then jumps at the opportunity to sneak past -- transcribing as it goes and transferring the histones upstream.
 
See how this might be another way of controlling RNA production, in tomorrow's issue of Science, July 31, 2009