Regulation of global translation during the cell cycle

Abstract

It is generally accepted that global translation varies during the cell cycle and is low in mitosis. However, addressing this issue is challenging because it involves cell synchronization, which evokes stress responses which, in turn, affect translation rates. Here we have used two approaches to measure global translation rates in different cell-cycle phases. First, synchrony in different cell-cycle phases was obtained involving the same stress, by using temperature-sensitive mutants. Second, translation and DNA content were measured by flow cytometry in exponentially growing, single cells. We found no major variation in global translation rates through the cell cycle in either fission-yeast or mammalian cells. We also measured phosphorylation of eukaryotic initiation factor-2, an event thought to downregulate global translation in mitosis. In contrast with the prevailing view, eIF2 phosphorylation correlated poorly with downregulation of general translation and ectopically induced eIF2 phosphorylation inhibited general translation only at high levels.