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Histone deacetylase activity in conjunction with E2F‐1 and p53 regulates Apaf‐1 expression in 661W cells and the retina

2008; Wiley; Volume: 87; Issue: 4 Linguagem: Inglês

10.1002/jnr.21910

1097-4547

Deborah Wallace, Thomas G. Cotter,

NF-κB Signaling Pathways

Abstract Apaf‐1 and the cysteine proteases known as caspases are genes central to the intrinsic apoptotic pathway in the retina. Previously, we have shown that histone deacetylase (HDAC) activity regulates Apaf‐1 expression in the retina. In this study, we unravel the detailed molecular mechanism of HDAC‐mediated regulation of Apaf‐1 initially by use of a cell line (661W), which expresses some cone‐specific genes and then by means of an ex vivo retinal explant system. Inhibition of HDAC activity by trichostatin A (TSA) up‐regulates Apaf‐1 expression, which precedes the induction of apoptosis. Furthermore, by a bioinformatics approach, we identify E2F‐1 and p53 binding sites on the mouse Apaf‐1 promoter and show by chromatin immunoprecipitation assays that these sites are occupied in vitro and that treatment with TSA results in increased binding of E2F‐1 and p53 to the Apaf‐1 promoter. By performing siRNA to these transcription factors, we illustrate that they govern Apaf‐1 expression levels in vitro. Finally, in a retinal explant system, we show that similar to our 661W results, E2F‐1 and p53 are up‐regulated after inhibition of HDAC activity in the retina. This correlates with our previous observation in the explant system that Apaf‐1 expression increases significantly and leads to an induction of apoptosis after inhibition of HDAC activity. Overall, we propose a role for HDAC activity, E2F‐1, and p53 in the regulation of Apaf‐1 expression in 661W cells; initial data also indicate a regulatory role in the retina. © 2008 Wiley‐Liss, Inc.