Ribosome demand links transcriptional bursts to protein expression noise

The translation process modulates stochastic fluctuations in mRNA numbers
and determines noise in protein expression. Studies across different
organisms have revealed a positive correlation between translational
efficiency and protein noise. However, the molecular basis of this
correlation has remained unknown. Through stochastic modeling of
translation in single mRNA molecules and empirical measurement of protein
noise, we demonstrate that ribosome demand associated with high
translational efficiency leads to the correlation between translational
efficiency and protein noise. We also show that this correlation is
present only in promoters with bursty transcription, where ribosome demand
varies with stochastic fluctuations in mRNA numbers. Thus, our work shows
how transcriptional bursts are translated into protein noise, which has
implications for investigating noise and phenotypic heterogeneity across
biological systems.