SRC-3 deficiency-induced GCN5 downregulation is responsible for the defective phenotype and function of HSCs. (A) Relative messenger RNA expression levels of Nrf-1, Tfam, and Tfb1m in LT-HSCs from WT and SRC-3^−/− BM (n = 3 mice per group). All values are presented relative to WT controls. (B-C) Flow cytometric analysis of the MFI of (B) PGC-1α and (C) GCN5 in LT-HSCs from WT and SRC-3^−/− BM (n = 5 mice per group). (D) Western blot analysis of PGC-1α, p-PGC-1α, and GCN5 in WT and SRC-3^−/− LSKs (n = 5-6 mice per group were pooled). (E) Acetylation level of PGC-1α in WT and SRC-3^−/− LSKs (n = 6 mice per group were pooled). IP, immunoprecipitation; WB, western blot. (F-J) WT or SRC-3^−/− (CD45.2) LSKs (5 × 10³) transduced with control or GCN5, together with 5 × 10⁵ competitor BM cells (CD45.1), were transplanted into lethally irradiated (10 Gy) WT (CD45.1) recipients. Flow cytometric analysis of (F) mitochondrial mass, (G) mitochondrial membrane potential, (H) ROS levels, and (I) cell cycle in donor-derived (CD45.2) LT-HSCs in the CD45.1 recipients’ BM 16 weeks after transplantation (n = 6 mice per group). (J) The percentages of donor-derived cells (CD45.2) in the CD45.1 recipients’ PB 16 weeks after transplantation (n = 6 mice per group). *P < .05, **P < .01. (K) Schematic of proposed model demonstrating how SRC-3 regulates HSCs quiescence and function via its role on metabolism homeostasis.