Genome-wide screen for cell growth regulators in fission yeast

Cellular growth control is important for all living organisms, but experimental investigation into this problem is difficult because of the complex range of growth regulatory mechanisms. Here, we have used the fission yeast Schizosaccharomyces pombe to identify potential master regulators of growth. At the restrictive temperature, the S. pombe pat1(ts) mei4 Delta. strain enters the meiotic developmental program, but arrests in meiotic G2 phase as mei4(+) is essential for meiotic progression. These cells do not grow, even in an abundance of nutrients. To identify regulators of growth that can reverse this growth arrest, we introduced an ORFeome plasmid library into the pat1(ts) mei4 Delta. strain. Overexpression of eight genes promoted cell growth; two of these were core RNA polymerase subunits, and one was sck2(+), an S6 kinase thought to contribute to TORC1 signalling. Sck2 had the greatest effect on cell growth, and we also show that it significantly increases the cellular transcription rate. These findings indicate, for the first time, that global transcriptional control mediated through S6 kinase signalling is central to cellular growth control.