G-quadruplexes are promoter elements controlling nucleosome exclusion and RNA polymerase II pausing

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Eukaryotic promoter sequences remain difficult to universally define.
• Chromatin opening is essential for transcriptional machinery recruitment.
• The role of DNA elements in promoter opening is not fully understood.

Purpose of the Study:

• To investigate the role of G-quadruplex (G4) structures in eukaryotic promoter function.
• To determine if G4s contribute to promoter opening and transcriptional regulation.

Main Methods:

• Bioinformatic analysis to identify G4 enrichment at mammalian promoters.
• In vivo and in vitro experiments to assess nucleosome exclusion by G4s.
• Functional assays to evaluate the impact of G4 manipulation on transcription and chromatin structure.

Main Results:

• G-quadruplexes are highly enriched at mammalian promoters, correlating with maximum promoter activity.
• Experimental G4s effectively exclude nucleosomes and favor strong positioning.
• Impairing or destabilizing G4s reduces transcriptional activity, hinders chromatin opening, and affects RNA production.
• G4 stabilization reduces proximal promoter pausing.

Conclusions:

• G-quadruplexes function as critical promoter elements.
• G4s facilitate promoter opening by excluding nucleosomes.
• G4s promote transcriptional activation by facilitating RNA polymerase II pause-release.