Nature Genetics 38, 636 - 643 (2006)
Published online: 21 May 2006; | doi:10.1038/ng1807
Noise in protein expression scales with natural protein abundanceArren Bar-Even1, Johan Paulsson2, 3, Narendra Maheshri4, Miri Carmi1, Erin O'Shea4, Yitzhak Pilpel1
& Naama Barkai1, 51
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel. 2
Department of Systems Biology, Harvard University, Boston, Massachusetts 02115, USA. 3
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK. 4
Department of Molecular and Cellular Biology, Howard Hughes Medical Institute, Harvard University, 7 Divinity Avenue, Cambridge, Massachusetts 02138, USA. 5
Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
Correspondence should be addressed to Naama Barkai naama.barkai@weizmann.ac.il or Yitzhak Pilpel pilpel@weizmann.ac.il Noise in gene expression is generated at multiple levels, such as transcription and translation, chromatin remodeling and pathway-specific regulation. Studies of individual promoters have suggested different dominating noise sources, raising the question of whether a general trend exists across a large number of genes and conditions. We examined the variation in the expression levels of 43 Saccharomyces cerevisiae proteins, in cells grown under 11 experimental conditions. For all classes of genes and under all conditions, the expression variance was approximately proportional to the mean; the same scaling was observed at steady state and during the transient responses to the perturbations. Theoretical analysis suggests that this scaling behavior reflects variability in mRNA copy number, resulting from random 'birth and death' of mRNA molecules or from promoter fluctuations. Deviation of coexpressed genes from this general trend, including high noise in stress-related genes and low noise in proteasomal genes, may indicate fluctuations in pathway-specific regulators or a differential activation pattern of the underlying gene promoters.
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