The effects of molecular noise and size control on variability in the budding yeast cell cycle.

Journal Article (Journal Article)

Molecular noise in gene expression can generate substantial variability in protein concentration. However, its effect on the precision of a natural eukaryotic circuit such as the control of cell cycle remains unclear. We use single-cell imaging of fluorescently labelled budding yeast to measure times from division to budding (G1) and from budding to the next division. The variability in G1 decreases with the square root of the ploidy through a 1N/2N/4N ploidy series, consistent with simple stochastic models for molecular noise. Also, increasing the gene dosage of G1 cyclins decreases the variability in G1. A new single-cell reporter for cell protein content allows us to determine the contribution to temporal G1 variability of deterministic size control (that is, smaller cells extending G1). Cell size control contributes significantly to G1 variability in daughter cells but not in mother cells. However, even in daughters, size-independent noise is the largest quantitative contributor to G1 variability. Exit of the transcriptional repressor Whi5 from the nucleus partitions G1 into two temporally uncorrelated and functionally distinct steps. The first step, which depends on the G1 cyclin gene CLN3, corresponds to noisy size control that extends G1 in small daughters, but is of negligible duration in mothers. The second step, whose variability decreases with increasing CLN2 gene dosage, is similar in mothers and daughters. This analysis decomposes the regulatory dynamics of the Start transition into two independent modules, a size sensing module and a timing module, each of which is predominantly controlled by a different G1 cyclin.

Full Text

Duke Authors

Cited Authors

  • Di Talia, S; Skotheim, JM; Bean, JM; Siggia, ED; Cross, FR

Published Date

  • August 23, 2007

Published In

Volume / Issue

  • 448 / 7156

Start / End Page

  • 947 - 951

PubMed ID

  • 17713537

Electronic International Standard Serial Number (EISSN)

  • 1476-4687

Digital Object Identifier (DOI)

  • 10.1038/nature06072


  • eng

Conference Location

  • England