PROJECT SUMMARY/ABSTRACT
Aging is the leading risk factor for chronic diseases such as cardiovascular disease, cancer and
neurodegeneration. As the U.S. population continues to grow older, the prevalence of these diseases will
increase. Therefore, determining the mechanisms underpinning pro-longevity interventions, such as caloric
restriction (CR) is an important priority. Although CR intervention improves factors contributing to cellular demise
in the aging process, its impact on chromatin remodeling remains understudied. My dissertation is to understand
the establishment and maintenance of quiescent chromatin architecture in the context of Saccharomyces
cerevisiae chronological aging and its response to longevity interventions like CR. Understanding these changes
in chromatin organization will facilitate the development of novel interventions, mimicking the beneficial effects
of CR on longevity.
In preliminary experiments, I have found that CR optimizes transcription conditions with abundant intracellular
nucleotide, acetyl-CoA levels, and acetyl-CoA synthetase (Acs2), as cells start the transition into quiescence. I
propose to elucidate the mechanism of how these conditions induce a transcriptional regulatory cascade that
enhances quiescence. First in Aim 1, I will define how CR temporally and structurally enhances chromatin
compaction as cells enter quiescence. Second, I will test the hypothesis that CR induces the early wave of
transcription via acetyl-CoA accumulation by Acs2. This accumulation then results in histone hyperacetylation at
relevant target promoters by Gcn5 histone acetyltransferase complex (SAGA). Third, I will test the contribution
of nucleotide buffering to transcription and the later establishment of repressive chromatin in quiescence. These
studies will provide mechanistic insights of CR's role in establishing quiescence during chronological aging.
Chromatin compaction is vital to maintaining quiescence, yet the architectural changes that occur during aging
or in response to CR are unknown. Therefore, in Aim 2, I will characterize the maintenance of repressive
chromatin structure during chronological aging. I hypothesize that transcriptional repressors and chromatin
architectural proteins become depleted with age, and thus detrimental to quiescence. First, I will detect
breakdown of repressive chromatin structure in aged cells and its effect on transcription using a combination of
ATAC-Seq and PRO-Seq. Second, I will characterize the depletion of chromatin factors in CLS using tandem
mass tagging (TMT) experiments. Third, I will determine if chromatin openness during quiescence drives cell
cycle re-entry or cell death in snf1¿ and gcn5¿ mutants. These experiments will define CR's impact on the
temporal and structural maintenance of repressive chromosomal architecture during aging.