Asymmetric cell division requires specific mechanisms for adjusting global transcription

Abstract

Most cells divide symmetrically into two approximately identical cells. There are many examples, however, of asymmetric cell division that can generate sibling cell size differences. Whereas physical asymmetric division mechanisms and cell fate consequences have been investigated, the specific problem caused by asymmetric division at the transcription level has not yet been addressed. In symmetrically dividing cells the nascent transcription rate increases in parallel to cell volume to compensate it by keeping the actualmRNA synthesis rate constant. This cannot apply to the yeast Saccharomyces cerevisiae, where this mechanism would provoke a neverending increasing mRNA synthesis rate in smaller daughter cells.We show here that, contrarily to other eukaryotes with symmetric division, budding yeast keeps the nascent transcription rates of its RNA polymerases constant and increasesmRNAstability. This control on RNA pol II-dependent transcription rate is obtained by controlling the cellular concentration of this enzyme.