Modulation of Life-span by Histone Deacetylase Genes inSaccharomyces cerevisiae

Abstract

The yeast Saccharomyces cerevisiae has a limited life-span, which is measured by the number of divisions that individual cells complete. Among the many changes that occur as yeasts age are alterations in chromatin-dependent transcriptional silencing. We have genetically manipulated histone deacetylases to modify chromatin, and we have examined the effect on yeast longevity. Deletion of the histone deacetylase gene RPD3 extended life-span. Its effects on chromatin functional state were evidenced by enhanced silencing at the three known heterochromatic regions of the genome, the silent mating type (HM), subtelomeric, and rDNA loci, which occurred even in the absence of SIR3. Similarly, the effect of the rpd3Delta on life-span did not depend on an intact Sir silencing complex. In fact, deletion of SIR3 itself had little effect on life-span, although it markedly accelerated the increase in cell generation time that is observed during yeast aging. Deletion of HDA1, another histone deacetylase gene, did not result in life-span extension, unless it was combined with deletion of SIR3. The hda1Delta sir3Delta resulted in an increase in silencing, but only at the rDNA locus. Deletion of RPD3 suppressed the loss of silencing in rDNA in a sir2 mutant; however, the silencing did not reach the level found in the rpd3Delta single mutant, and RPD3 deletion did not overcome the life-span shortening seen in the sir2 mutant. Deletion of both RPD3 and HDA1 caused a decrease in life-span, which resulted from a substantial increase in initial mortality of the population. The expression of both of these genes declines with age, providing one possible explanation for the increase in mortality during the life-span. Our results are consistent with the loss of rDNA silencing leading to aging in yeast. The functions of RPD3 and HDA1 do not overlap entirely. RPD3 exerts its effect on chromatin at additional sites in the genome, raising the possibility that events at loci other than rDNA play a role in the aging process.

Life extension in Drosophila by feeding a drug

“…We observed both induction and repression of transcription by PBA. It is interesting to note that overexpression of Sir2 protein in both yeast (26) and C. elegans (40), which has NAD-dependent histone deacetylase activity, is implicated in silencing of gene transcription, associated with extension of the lifespan, whereas deletion of a different histone deacetylase (RPD3) also extends lifespan (27). This conundrum suggests that the underlying mechanism for the extension of lifespan may be an optimal balance of expression and repression of various genes to regulate an optimal physiological and cellular environment for longevity.…”

Rtg2 Protein Links Metabolism and Genome Stability in Yeast Longevity

“…The rDNA is associated with yeast aging (Kennedy et al 1997;Sinclair and Guarente 1997;Kim et al 1999a;Benguria et al 2003). RAD52-dependent recom- old yeast cells (Sinclair and Guarente 1997).…”

“…To generate the fob1 this theory, however. Furthermore, recent data have deletion strains, an EcoRI-BamHI fragment of plasmid pCB6, revealed that accumulation of ERCs is not an obligatory which contains the kanamycin gene flanked by the 5Ј-region feature but rather parallels aging (Ashrafi et al 1999; (Ϫ592 to Ϫ34) and the 3Ј-region (ϩ1707 to ϩ1893) of the Heo et al 1999;Kim et al 1999a).…”

Regulation of Telomere Length by Fatty Acid Elongase 3 in Yeast

“…Analysis of Replicative Life Span in Yeast-The replicative life span was analyzed as described previously (27). In summary, new buds (virgin cells) from overnight cultures were deposited in a row in isolated spots on an YPD plate.…”

“…Yeast cultures were grown for 4 -5 days until they reach a stationary phase in 10 ml of YPD media. Then, the cells were washed twice, and an equal number of cells were re-suspended in 10 ml of sterile distilled water, and their growth was monitored on YPD plates after serial dilutions.Analysis of Replicative Life Span in Yeast-The replicative life span was analyzed as described previously (27). In summary, new buds (virgin cells) from overnight cultures were deposited in a row in isolated spots on an YPD plate.…”