Propagation of RNA polymerase copy number variation to downstream protein expression noise in bacterial cells
* SPEAKERS
Name
Affiliation
E-mail
Nam Ki Lee
POSTECH
* HOST(Applicant)
Name
Affiliation
E-mail
Junghyo Jo
APCTP
jojunghyo(at)apctp.org
* DATE / TIME
2015-03-20, 11:00am
* ABSTRACT
Cell-to-cell variation resulting from noise in gene expression is a general phenomenon in cells, which often determines a cell’s variability, adaptation, and fate. Transcription, i.e., the process of generating mRNA, is the key stage of noise generation in cells. However, how the noise, or variation, in RNA polymerase (RNAP) copy numbers is propagated to downstream gene expression noise remains unknown. Here, we quantitatively investigated this question by monitoring how the noises in the expression of two fluorescent protein reporter genes driven by the T7 RNAP promoters varied with the concentration of T7 RNAP. We found that intrinsic noise was independent of RNAP noise, whereas extrinsic noise scaled linearly with RNAP noise. The propagation of RNAP noise to downstream protein noise was inversely proportional to the RNAP concentration, which suggests that the propagation of RNAP noise is determined by the fraction of the promoter that is not occupied by RNAP. When the RNAP concentration was saturated, the total noise was reduced to 0.03, which corresponds to only 30% of the lower noise limit in E. coli. This result suggests that the noise generated during transcription is the dominant source of extrinsic noise for high-copy-number proteins in bacteria.
