Friday, June 7, 2013

Location and timing control of Pol2 promoter-proximal pausing

Kinetic Competition between Elongation Rate and Binding of NELF Controls Promoter-Proximal Pausing
Jian Li, Yingyun Liu, Ho Sung Rhee, Saikat Kumar B. Ghosh, Lu Bai, B. Franklin Pugh, David S. Gilmour

Several significant conclusions: 
First, core promoters of protein-coding genes throughout theDrosophila genome contain little or no open Pol II promoter complexes. Thus immediately after assembly of the transcription complex at the core promoter, Pol II rapidly initiates and elongates into a paused state that precludes assembly of a second polymerase into an initiation complex. snRNA genes encoding components of the spliceosome and the induced heat shock genes are exceptional in that open Pol II promoter complexes are evident on these genes. 
Second, the location of the pause can be altered by perturbing the kinetics of elongation or the levels of pausing factors, suggesting that the location of the pause depends on a kinetic competition between elongation and the binding of these factors. 
Third, GAF tips this kinetic competition in favor of pausing by recruiting NELF to the promoter.

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