Synchronized budding of yeast cells following X-irradiation

Abstract

Yeast cells, following a continuous 180 minute treatment with X-radiation which inhibited cell division but not growth, resumed budding in a synchronous fashion. Though budding was resumed, cell separation did not occur, and consequently, groups of four cells resulted from budding of the paired cells typical of the stage of inhibited division. A second budding produced still larger cell groups. Measurements of the uptake of radioactive phosphorus by division-inhibited cells and by cultures with 80 per cent of the cells ready to bud showed a greater uptake per unit of dry weight by the inhibited cells. The total phosphorus and the phosphorous content of various separated fractions were higher in inhibited cells than in cells ready to bud. Insoluble polyphosphates of inhibited cells showed an accelerated uptake, while soluble polyphosphates took up radioactive phosphorus at a slower rate. Nucleic acids showed no reduced uptake. These phosphorus differences, including the possible specific involvement of polyphosphates in budding processes, are considered as leads in uncovering the specific reactions affected by radiation in the processes of cell division.