Two-step, Extensive Alterations in the Transcriptome from G0 Arrest to Cell Division in Schizosaccharomyces pombe

Body cells in multi-cellular organisms are in the G0 state, in which cells are arrested and terminally differentiated. To understand how the G0 state is maintained, the genes that are specifically expressed or repressed in G0 must be identified, as they control G0. In the fission yeast Schizosaccharomyces pombe, haploid cells are completely arrested under nitrogen source starvation with high viability. We examined the global transcriptome of G0 cells and cells on the course to resume vegetative growth. Approximately 20% of the transcripts of ~5000 genes increased or decreased more than 4-fold in the two-step transitions that occur prior to replication. Of the top 30 abundant transcripts in G0, 23 were replaced by ribosome- and translation-related transcripts in the dividing vegetative state. Eight identified clusters with distinct alteration patterns of ~2700 transcripts were annotated by Gene Ontology. Disruption of 53 genes indicated that 9 of them were necessary to support the proper G0 state. These 9 genes included two C2H2 zinc finger transcription factors, a cyclin-like protein implicated in phosphorylation of RNA polymerase II, two putative autophagy regulators, a G-protein activating factor, and two CBS domain proteins, possibly involved in AMP-activated kinase. Keywords: Keywards: Time course, Nitrogen starvation, G0 state, Nitrogen replenishment, Nutrient signal, Cell cycle, Cell proliferation Gene expression profile during the resumption of cell growth and division from the nitrogen-starved G0 state in fission yeast. Type of experiment: Comparing the growth-resuming cells in each experimental condition with cells at nitrogen-starved G0 state. Also compairing the vegetatively-growing cells with nitrogen-starved G0 cells. Experimental factor: Time course after nitrogen replenishment. Quality control steps taken: Experiments were not repeated. The time course data mostly showed gradual and successive alteration. Little contradiction were apparent among them. Northern hybridization analysis was done on 56 genes for confirmation. (35 cases showed consistent results.)