| SAT1 (spermidine/spermine N¹-acetyltransferase 1, SSAT1) is a cytosolic acetyltransferase of the polyamine catabolic pathway that catalyzes the transfer of acetyl groups from acetyl‑CoA to spermidine and spermine, functions as the rate‑limiting step in polyamine interconversion, and controls intracellular polyamine pools that influence nucleic acid interactions, signaling, and cell survival programs. The enzyme belongs to the GNAT acetyltransferase family and contains a central acetyl‑CoA–binding fold with conserved catalytic residues that align the acetyl donor and polyamine acceptor, flanked by regions that determine substrate specificity and provide surfaces for interaction with other proteins and possibly chromatin-associated complexes. Catalytic activity targets spermidine and spermine with high efficiency and also acts on related diamines, generating N¹‑acetylated products that are substrates for polyamine oxidase and that can be exported from the cell, so SAT1 activity simultaneously decreases higher polyamine species, increases lower polyamines such as putrescine, and facilitates polyamine efflux. These reactions position SAT1 as a core regulator of polyamine homeostasis that adjusts the balance between synthesis and catabolism in response to metabolic and stress signals, and that shapes the availability of polyamines for binding to DNA, RNA, and proteins. Transcriptional and post-transcriptional control of SAT1 expression is rapid and robust, allowing strong induction by elevated polyamines, oxidative and genotoxic stress, and other signaling pathways, which produce transient surges in acetyltransferase activity that remodel polyamine pools and modify downstream cellular responses. SAT1 also functions as a gene-specific transcriptional regulator through local acetylation of promoter-associated polyamines, with chromatin-bound SAT1 found at defined target promoters where its catalytic activity supports expression of cell-cycle regulators and DNA damage response genes. In aggressive brain tumors, including high-grade gliomas, SAT1 expression is elevated, and correlates with enhanced expression of DNA repair and cell-cycle programs, maintenance of neurosphere stem-like properties, and resistance to radiotherapy, and SAT1-dependent polyamine acetyltransferase activity is required for these transcriptional and phenotypic effects. SAT1 interacts with transcriptional regulators such as FOXM1 and EZH2 at the MELK promoter and related loci, where polyamine acetylation contributes to a chromatin environment permissive for expression of oncogenic networks, linking a classical metabolic enzyme directly to epigenetic and transcriptional control. |
Lane 1: 293T, Lane 2: 293T (SAT1(human) transfected)
