The role of p53 deacetylation in p21Waf1 regulation by laminar flow

Laminar flow arrests vascular endothelial cells at the G(0)/G(1) phase with concurrent increase in p53 and p21(Waf1). We investigated the molecular mechanism by which laminar flow activates p53 and p21(Waf1) in endothelial cells. The application of a laminar flow (12 dyn/cm(2)) increased the deacetylation at Lys-320 and Lys-373 of p53 and the acetylation at Lys-382 in human umbilical vein endothelial cells. Laminar flow increased the activity of histone deacetylase (HDAC) and the association of p53 with HDAC1. Treating human umbilical vein endothelial cells with trichostatin A (TSA), an HDAC inhibitor, abolished the flow-induced p53 deacetylation at Lys-320 and Lys-373. To investigate the role of the HDAC-deacetylated p53 in the flow activation of p21(Waf1), we found that TSA inhibited the activation at both the mRNA and protein levels. Deletion and mutation analyses of the p21(Waf1) promoter revealed that flow activated p21(Waf1) through p53 and TSA abrogated this p53-dependent activation. The expression plasmid encoding the p53 mutant, with Lys-320 and Lys-373 replaced by Arg, increased the activity of the co-transfected p21(Waf1) promoter, which demonstrates that HDAC-deacetylated p53 can transactivate the p21(Waf1) gene. The regulation of the p53-p21(Waf1) pathway by laminar flow was further supported by observations that flow caused an increase of p21(Waf1) level in the wild-type HCT116 (p53(+/+)) cells but not in the p53-null HCT116 cells.