Cell-Cycle Perturbations Suppress the Slow-Growth Defect of spt10Δ Mutants in Saccharomyces cerevisiae

Spt10 is a putative acetyltransferase of Saccharomyces cerevisiae that directly activates the transcription of histone genes. Deletion of SPT10 causes a severe slow growth phenotype, showing that Spt10 is critical for normal cell division. To gain insight into the function of Spt10, we identified mutations that impair or improve the growth of spt10 null (spt10 Delta) mutants. Mutations that cause lethality in combination with spt10 Delta include particular components of the SAGA complex as well as asf1 Delta and hir1 Delta. Partial suppressors of the spt10 Delta growth defect include mutations that perturb cell-cycle progression through the G1/S transition, S phase, and G2/M. Consistent with these results, slowing of cell-cycle progression by treatment with hydroxyurea or growth on medium containing glycerol as the carbon source also partially suppresses the spt10 Delta slow-growth defect. In addition, mutations that impair the Lsm1-72Pat1 complex, which regulates decapping of polyadenylated mRNAs, also partially suppress the spt10 Delta growth defect. Interestingly, suppression of the spt10 Delta growth defect is not accompanied by a restoration of normal histone mRNA levels. These findings suggest that Spt10 has multiple roles during cell division.