Transcriptional temporal noise in yeast genome 397 Genetics and Molecular Research 6 (2): 397-414 (2007) www.funpecrp.com.br Minimization of transcriptional temporal noise and scale invariance in the yeast genome R.C. Ferreira 1 *, F. Bosco 1 *, P.B. Paiva 2 and M.R.S. Briones 1 1 Departamento de Microbiologia, Imunologia e Parasitologia, 2 Departamento de Informática em Saúde, Universidade Federal de São Paulo, São Paulo, SP, Brasil *These authors contributed equally to this study. Corresponding author: M.R.S. Briones E-mail: marcelo@ecb.epm.br Genet. Mol. Res. 6 (2): 397-414 (2007) Received February 6, 2007 Accepted April 16, 2007 Published June 29, 2007 ABSTRACT. The analysis of transcriptional temporal noise could be an interesting means to study gene expression dynamics and stochasticity in eukaryotes. To study the statistical distributions of temporal noise in the eukaryotic model system Saccharomyces cerevisiae, we analyzed microarray data corresponding to one cell cycle for 6200 genes. We found that the temporal noise follows a lognormal distribution with scale invariance at the genome, chromosomal and sub-chromosomal levels. Correlation of temporal noise with the codon adaptation index suggests that at least 70% of all protein-coding genes are a noise minimization core of the genome. Accordingly, a mathematical model of individual gene expression dynamics was proposed, using an operator theoretical approach, which reveals strict conditions for noise variability and a pos- sible global noise minimization/optimization strategy at the genome level. Our model and data show that minimal noise does not correspond to genes obeying a strictly deterministic dynamics. The natural strategy of minimization consists in equating the mean of the absolute value of the relative variation of the expression level (α) with noise (η). We hypoth- Genetics and Molecular Research 6 (2): 397-414 (2007) FUNPEC-RP www.funpecrp.com.br