Isotropic Order Among a Core Set of Cell-Cycle Transcripts Conserved Between Budding and Fission Yeast

• Activity Number: 25
• Type: Contributed
• Date/Time: Sunday, July 31, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Biometrics Section
• Author(s): Shyamal D. Peddada*+ and Miguel Fernández and Cristina Rueda
• Companies: National Institute of Environmental Health Sciences and Universidad de Valladolid and Universidad de Valladolid
• Keywords: Cell division cycle ; Conditional test ; Constrained estimation ; Conservation of isotropic order ; Saccharomyces Cerevisiae ; Schizosaccharomyces Pombe

Abstract

A cell division cycle in eukaryotes is a well coordinated process where cells go through 4 distinct phases before dividing. Genes with periodic expression are known as cell-cycle genes. To discover evolutionarily conserved cell-cycle genes, biologists are interested in identifying genes that are periodic in multiple organisms. There has been considerable discussion in the literature on genes that are periodic in fission yeast (S. pombe) as well as in budding yeast (S. cerevisiae). Based on recent microarray studies, a conservative estimate of the number of genes that are periodic in both yeasts is 35 (known as a "core set"). Phase angle of peak expression of a cell-cycle gene is of interest as it may be associated with its function. Since the cell cycle is a carefully orchestrated process, we hypothesize that the relative order of the phase angles (isotropic order) among the core set of genes is conserved in the two yeasts. Using a novel statistical methodology, we demonstrate that the isotropic order is conserved for at least 80% of genes in the core set. Surprisingly at most 33% of fission yeast genes appear to satisfy the isotropic order of the corresponding human orthologs.