Global Transcriptome Analysis Reveals That Poly(ADP-Ribose) Polymerase 1 Regulates Gene Expression through EZH2

Area of Science:

• Epigenetics and Gene Regulation
• Molecular Biology
• Biochemistry

Background:

• Posttranslational modifications, including poly(ADP-ribosyl)ation (PARylation), are crucial for regulating chromatin-modifying enzymes and gene expression.
• Poly(ADP-ribose) polymerase (PARP) is a key enzyme involved in DNA repair and other cellular processes, but its role in global gene regulation is not fully understood.

Purpose of the Study:

• To investigate the role of poly(ADP-ribose) polymerase (PARP) in global gene expression in a lymphoblastoid B cell line.
• To elucidate the molecular mechanisms by which PARP influences gene regulation, particularly its interaction with chromatin-modifying enzymes.

Main Methods:

• Inhibition of PARP catalytic activity using olaparib.
• Gene expression analysis using transcriptomics.
• Gene ontology analysis.
• Pharmacological inhibition and knockdown of PARP1.
• Chromatin immunoprecipitation (ChIP) assays.
• Analysis of EZH2 promoter occupancy by transcription factors.

Main Results:

• PARP inhibition led to global gene deregulation, affecting approximately 11% of expressed genes.
• PARP inhibition induced the expression of EZH2 (a Polycomb Repressive Complex 2 member), increasing global H3K27me3 levels.
• PARP1 inhibition resulted in H3K27me3 deposition at EZH2 target genes, causing gene silencing.
• Increased EZH2 expression was linked to reduced occupancy of the repressor E2F4 at the EZH2 promoter.

Conclusions:

• PARP plays a significant role in global gene regulation.
• This study identifies a direct role for PARP1 in regulating EZH2 expression and function, linking PARP activity to epigenetic silencing via H3K27 trimethylation.