p73 competes with co-activators and recruits histone deacetylase to NF-Y in the repression of PDGF β-receptor

Abstract

We investigated mechanisms of the p73α-mediated repression of the platelet-derived growth factor β-receptor (PDGFRB) promoter caused by its interaction with NF-Y. Treatment of cells with the histone deacetylase (HDAC) inhibitor, Trichostatin A, increases PDGFRB promoter activity through the CCAAT motif and counteracts the repression caused by p73α. Activation of the PDGFRB promoter by the co-activator p300 also occurs through the CCAAT motif. Expression of p73α counteracts both p300- and P/CAF-mediated activation of the PDGFRB promoter, and expression of p300 or P/CAF attenuates the p73α-mediated repression of the promoter activity. In concordance, p73α decreases the p300-mediated acetylation of NF-YC, p300 competes with p73α for binding NF-YB, and P/CAF competes with p73α for binding NF-YB and NF-YC. Furthermore, p73α, but not the oncogenic ΔNp73α, binds directly to HDAC1. We performed chromatin immunoprecipitation with antibodies against p73, ΔNp73, NFYB, p300 and HDAC1 at different periods after serum stimulation in serum-starved NIH3T3 cells. A marked decrease of ΔNp73, NF-YB and p300 was detected 6 hours after serum stimulation when the expression of PDGFRB decreased. Conversely, HDAC1 was found bound at its maximum and the anti-p73 detecting both TAp73 and ΔNp73 was found at all time points, indicating that p73, but not ΔNp73, remains bound at this time. Double immunofluorescence staining of TAp73 and HDAC1 revealed that both of these molecules exist in the nucleus at this time point, supporting the presence of endogenous interaction. These results suggest that p73 and ΔNp73 behave as physiological regulators for the transcription of the PDGFRB promoter.