For distribution - thanks

[CM ICTP - Trieste]

CONDENSED MATTER AND STATISTICAL PHYSICS SECTION

	
INFORMAL SEMINAR  on  Statistical Physics



Monday, 20 August    -    5:00 p.m.



Seminar Room  - Main Building (first floor)



T.B. LIVERPOOL   (University of Leeds)



" Fluctuations, pauses and backtracking in DNA transcription "


Abstract

Transcription is a vital stage in the process of gene expression and a 
major contributor to fluctuations in gene expression levels for which 
it is typically modelled as a single step process with Poisson 
statistics.  However, recent single molecule experiments raise 
questions about the validity of such a simple single step picture.  We 
present a molecular multi-step model of transcription elongation that 
demonstrates that transcription times are in general non-Poisson 
distributed.  In particular, we model transcriptional pauses due to 
backtracking of the RNA polymerase as a first passage process.  By 
including such pauses, we obtain a broad, heavy-tailed distribution of 
transcription elongation times.  When transcriptional pauses result in 
long transcription times,  we demonstrate that this naturally leads to 
bursts of mRNA production and non-Poisson statistics of mRNA levels.  
These results suggest that transcriptional pauses may be a significant 
contributor to the variability in transcription rates with direct 
implications for noise in cellular processes as well as variability 
between cells.