PKR regulates quiescence and cell-cycle progression of HSPCs. (A) Flow cytometry analysis of DNA content and Ki67 expression in Lin⁻c-Kit⁺ BM cells from WT, TgPKR, TgDNPKR, or PKRKO mice. Numbers on the plot are the frequency of cells in the indicated cell-cycle phases. (B) Proliferation of Lin⁻c-Kit⁺ BM cells from WT, TgPKR, TgDNPKR, or PKRKO mice in vitro under standard growth conditions was measured by flow cytometry (n = 5). (C) Western blotting of Lin⁻c-Kit⁺ BM cells from WT, TgPKR, TgDNPKR, or PKRKO mice to investigate the mechanisms of PKR-dependent proliferation and cell cycle regulation. The cells from 5 mice for each genotype were pooled for western blotting. (D) Differentiation of Lin⁻c-Kit⁺ cells from WT, TgPKR, TgDNPKR, or PKRKO mice into CD11b⁺Gr1⁺ cells was measured by flow cytometry after culture under standard growth conditions.