Specific early-G1 blocks accompanied with stringent response in Saccharomyces cerevisiae lead to growth arrest in resting state similar to the G0 of higher eucaryotes

Abstract

Growth arrests of Saccharomyces cerevisiae cells in early G1 phase brought by various means were classified into two types according to the mode of growth recovery after release of the restraints against growth. The first type, including arrests caused by cdc25, cdc33, cdc35, and ils1 mutations at the nonpermissive temperature and also by sulfur starvation, showed a subsequent delay in the onset of budding when shifted back to permissive conditions. The length of the delay was positively correlated with the time that cells had been arrested. The second type, including those caused by cdc28 and cdc24 mutations and by α factor, did not affect the mode of growth recovery after the shift to permissive conditions irrespective of the time that cell proliferation had been restricted. Growth arrests of the first type seem to allow yeast cells to enter a resting state equivalent to the G0 state of higher eucaryotes because features of the G0 shown with lymphocytes and other cultured cells including unusually long delay before the growth recovery appeared to be associated with this type. We have noted that arrests of the first type were always accompanied with a stringent response of macromolecular synthesis and its partial release by cycloheximide. Mapping of arrest points along the path of the cell cycle by the reciprocal shift experiment suggested that arrest points in G1 that led to the G0-like arrest precede or are near the step sensitive to α-factor.