A Combinatorial Regulatory Platform Determines Expression of RNA Polymerase III Subunit RPC7α (POLR3G) in Cancer

Area of Science:

• Molecular Biology
• Cancer Genomics
• Gene Regulation

Background:

• The RNA polymerase III (Pol III) subunit RPC7α, encoded by POLR3G, is implicated in tumor growth and metastasis.
• Elevated POLR3G expression serves as a negative prognostic indicator across various cancer types.
• Mechanisms driving POLR3G upregulation in cancer remain largely undefined.

Purpose of the Study:

• To conduct a comprehensive genomic analysis to identify key regulators of POLR3G expression in cancer.
• To elucidate the molecular mechanisms contributing to POLR3G upregulation in malignant cells.

Main Methods:

• Large-scale genomic survey of mRNA and chromatin signatures.
• Identification and functional validation of transcription factors (TFs) influencing POLR3G.
• Analysis of epigenetic modifications, including DNA methylation and histone demethylation (KDM5B).
• Investigation of regulatory interactions, such as MXD4's role in disrupting MYC-driven expression.

Main Results:

• Discovered positive determinants of POLR3G expression, including a super-enhancer with multiple TFs.
• Identified negative determinants such as gene-internal DNA methylation and MXD4-mediated repression.
• Validated novel TFs (ZNF131, ZNF207) that enhance POLR3G expression.
• Showed MXD4 potentially inhibits MYC-driven POLR3G expression.
• Highlighted KDM5B as a potential influencer of POLR3G gene activity via chromatin modification.

Conclusions:

• POLR3G expression is regulated by a complex interplay of multiple factors and dynamic regulatory programs.
• Findings expand the understanding of the regulatory circuitry controlling POLR3G upregulation in cancer.
• Elucidating these mechanisms provides a foundation for exploring therapeutic strategies targeting POLR3G in cancer treatment.