ACSS2 drives senescence-associated secretory phenotype by limiting purine biosynthesis through PAICS acetylation

Senescence-associated secretory phenotype (SASP), an established feature of cellular senescence, mediates the biological effects of senescent cell on tissue microenvironment and contributes to aging-associated disease progression. The metabolic enzyme ACSS2 produces acetyl-CoA from acetate and epigenetically regulates gene expression through histone acetylation. Whether and how ACSS2 regulates cellular senescence through non-histone acetylation mechanisms remain unclear. Here we show that ACSS2 drives SASP by promoting PAlCS acetylation to restrain purine metabolism. Genetic and pharmacological inhibition, as well as deletion of Acss2 in mice blunts SASP gene expression and abrogates the pro-tumorigenic and immune surveillance functions of senescent cells. Mechanistically, ACSS2 directly interacts and promotes acetylation of PAlCS, a key enzyme for purine metabolism. The acetylation of PAlCS promotes autophagy-mediated degradation of PAlCS to limit purine metabolism and reduces dNTP pools for DNA repair, which exacerbates cytoplasmic chromatin fragment (CCF) accumulation and SASP. Altogether, our work links ACSS2-mediated local acetyl-CoA generation to purine metabolism through PAlCS acetylation that dictates the functionality of SASP, and identify ACSS2 as a potential senomorphic target for healthy aging and to prevent senescence-associated diseases. Overall design: To investigate how ACSS2 regulates cellular senescence, we established oncogene-induced senescent IMR90 cells in which ACSS2 has been knocked down by shRNA. We then performed transcriptomic profiling using RNA-seq data of 3 groups of cells including proliferating, senescent cells with and without ACSS2 knockdown.