p53 down-regulates SETDB1 gene expression during paclitaxel induced-cell death

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• Paclitaxel (PTX) is a chemotherapy drug known for inducing tubulin stability and regulating cancer cell death.
• While PTX's anticancer mechanisms are established, its impact on chromatin remodeling factors remains unclear.
• SETDB1 (SET domain bifurcated 1) is a histone methyltransferase implicated in gene silencing.

Purpose of the Study:

• To investigate the effect of Paclitaxel (PTX) on the expression of SETDB1 HMTase during cancer cell death.
• To elucidate the molecular mechanisms underlying PTX-induced changes in SETDB1 expression.

Main Methods:

• Human lung cancer cells were treated with PTX to induce G2/M arrest and cell death.
• Quantitative analysis of SETDB1 mRNA and protein levels.
• Luciferase reporter assays to assess SETDB1 promoter activity.
• p53 transfection and chromatin immunoprecipitation (ChIP) assays to study protein-DNA interactions and histone modifications.
• Immunoprecipitation to detect protein-protein interactions.

Main Results:

• PTX treatment induced p53 protein expression and significantly down-regulated SETDB1 at both transcriptional and protein levels.
• SETDB1 promoter activity, normally high, was markedly inhibited by PTX treatment.
• p53 transfection alone inhibited SETDB1 promoter activity.
• p53 directly bound to the SETDB1 promoter, leading to increased H3K9me3 (histone H3 lysine 9 trimethylation) occupancy.
• p53 was found to interact with SUV39H1, a key enzyme in H3K9me3 deposition.

Conclusions:

• PTX down-regulates SETDB1 gene expression in human lung cancer cells via a p53-dependent pathway.
• p53 mediates heterochromatic repression at the SETDB1 promoter by interacting with SUV39H1, increasing H3K9me3 levels and inhibiting transcription.