Plat-E retroviral packaging cells (28) were used to generate retroviral supernatants using PEIPro transfection reagent (Polyplus, Ullkirch, France) at a 3:1 PEIPro/DNA ratio. Supernatant containing virus was collected 48 hours after transfection.

Differentiation of myeloid progenitor cells into macrophages is accompanied by increased PU.1 concentration and increasing cell cycle length, culminating in cell cycle arrest. Induction of PU.1 expression in a cultured myeloid cell line expressing low PU.1 concentration results in decreased levels of mRNA encoding ATP-Citrate Lyase (ACL) and cell cycle arrest. ACL is an essential enzyme for generating acetyl-CoA, a key metabolite for the first step in fatty acid synthesis and for histone acetylation. We hypothesized that ACL may play a role in cell cycle regulation in the myeloid lineage. In this study, we found that acetyl-CoA or acetate supplementation was sufficient to rescue cell cycle progression in cultured BN cells treated with an ACL inhibitor or induced for PU.1 expression. Acetyl-CoA supplementation was also sufficient to rescue cell cycle progression in BN cells treated with a fatty acid synthase (FASN) inhibitor. We demonstrated that acetyl-CoA was utilized in both fatty acid synthesis and histone acetylation pathways to promote proliferation. Finally, we found that Acly mRNA transcript levels decrease during normal macrophage differentiation from bone marrow precursors. Our results suggest that regulation of ACL activity is a potentially important point of control for cell cycle regulation in the myeloid lineage.