Inhibition of mitogenesis in Balb/c-3T3 cells by trichostatin A - Multiplealterations in the induction and activation of cyclin-cyclin-dependent kinase complexes

Trichostatin A (TSA), a global repressor of histone deacetylase activity, i nhibits the proliferation of a number of cell types. However, the identific ation of the mechanisms underlying TSA-mediated growth arrests has remained elusive. In order to resolve in more detail the cellular process modulated during the growth inhibition induced by TSA, me studied the effect of the drug on G(0)/G(1) traverse in mitogen-stimulated quiescent Balb/c-3T3 cells . Cyclin D1 and retinoblastoma proteins were induced following the mitogeni c stimulation of both control and TSA-treated cells, and cyclin D1 formed c omplexes with CDK4 under both conditions. However, cyclin D1-associated kin ase was not increased in growth-arrested cells. The lack of cyclin D-associ ated kinase was paralleled by an accumulation of RE in a hypophosphorylated form, as would be expected. In contrast, p130 became partially phosphoryla ted, accompanied by a marked increase in p130-dependent E2F DNA binding act ivity and a partial release of free E2F-4, Despite the presence of E2F comp lexes not bound to pocket proteins, late G(1) EaF-dependent gene expression was not observed, The lack of cyclin D1-associated kinase in TSA-treated c ultures was potentially due to high levels of the cyclin-dependent inhibito r p27(kip1). However, the modulation of p27(kip1) levels by the deacetylase inhibitor cannot be responsible for the induction of the cell cycle arrest , since the growth of murine embryo fibroblasts deficient in both p27(kip1) and p21(cip1) was also inhibited by TSA, These data support a model in whi ch TSA inhibits very early cell cycle traverse, which, in turn, leads to a decrease in cyclin D1-associated kinase activation and a repression of late cell cycle-dependent events. Alterations in early G(0)/G(1) gene expressio n accompany the TSA-mediated growth arrest.