Gene duplication and neofunctionalization: POLR3G and POLR3GL

Area of Science:

• Molecular Biology
• Genetics
• Gene Regulation

Background:

• RNA polymerase III (Pol III) exists in two forms, utilizing either POLR3G or POLR3GL subunits.
• The functional and target gene specificity differences between these two Pol III forms remain unclear.

Purpose of the Study:

• To investigate the functional similarities and differences between POLR3G- and POLR3GL-containing Pol III.
• To determine if these two Pol III forms recognize the same target genes.
• To understand the evolutionary origin and regulatory mechanisms of these Pol III variants.

Main Methods:

• Analysis of gene duplication events for POLR3G and POLR3GL.
• Detection of POLR3G- and POLR3GL-containing Pol III in cell lines and mouse liver.
• Genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) to identify Pol III target genes.
• Promoter analysis to investigate transcription factor binding (MYC).

Main Results:

• POLR3G and POLR3GL arose from a vertebrate gene duplication event.
• Both POLR3G- and POLR3GL-containing Pol III are present in cells and tissues, with varying relative abundance.
• Both Pol III forms bind to the same target genes with consistent proportions within a cell line.
• The POLR3G promoter, unlike POLR3GL, binds the transcription factor MYC.

Conclusions:

• POLR3G and POLR3GL duplication resulted in similar target gene specificity for both Pol III forms.
• Neo-functionalization occurred at the transcription unit level, leading to differential regulation.
• These distinct regulatory mechanisms likely enhance the overall gene regulation potential of the cell.