Abstract
Episodic gene expression, with periods of high expression separated by periods of no
expression, is a pervasive biological phenomenon. This bursty pattern of expression draws from
a finite reservoir of expression machinery in a highly time variant way – i.e. requiring no
resources most of the time but drawing heavily on them during short intense bursts – that
intimately links expression bursting and resource sharing. Yet most recent investigations have
focused on specific molecular mechanisms intrinsic to the bursty behavior of individual genes,
while little is known about the interplay between resource sharing and global expression
bursting behavior. Here we confine E. coli cell extract in both cell-sized microfluidic chambers
and lipid-based vesicles to explore how resource sharing influences expression bursting.
Interestingly, expression burst size, but not burst frequency, is highly sensitive to the size of the
shared transcription and translation resource pools. The intriguing implication of these results is
that expression bursts are more readily amplified than initiated, suggesting burst formation
occurs through positive feedback or cooperativity. When extrapolated to prokaryotic cells,
these results suggest that large translational bursts may be correlated with large transcriptional
bursts. This correlation is supported by recently reported transcription and translation bursting
studies in E. coli. The results reported here demonstrate a strong intimate link between global
expression burst patterns and resource sharing, and suggest that bursting plays an important
role in optimizing the use of limited, shared expression resources.
