H3K4me3 regulates RNA polymerase II promoter-proximal pause-release

Area of Science:

• Epigenetics
• Molecular Biology
• Gene Regulation

Background:

• Histone H3 lysine 4 trimethylation (H3K4me3) is linked to transcriptional start sites.
• The precise function of H3K4me3 in transcription is unclear due to complex SET1/COMPASS methyltransferase roles.

Purpose of the Study:

• To investigate the specific role of H3K4me3 in transcriptional regulation using mouse embryonic stem cells.
• To determine whether H3K4me3 regulates transcription initiation, elongation, or both.

Main Methods:

• Acute ablation of SET1/COMPASS complex subunits in mouse embryonic stem cells.
• Analysis of H3K4 methylation states (H3K4me1, H3K4me2, H3K4me3) and their turnover rates.
• Assessment of transcriptional output, RNA polymerase II (RNAPII) pausing, and elongation dynamics.
• Investigation of the role of KDM5 demethylases in H3K4me3 turnover.
• Examination of the recruitment of integrator complex subunit 11 (INTS11).

Main Results:

• Complete loss of H3K4 methylation upon SET1/COMPASS complex ablation.
• H3K4me3 exhibits faster turnover than H3K4me1/H3K4me2 and depends on KDM5 demethylases.
• Loss of H3K4me3 did not affect transcriptional initiation but decreased transcriptional output.
• Increased RNAPII pausing and slower elongation were observed in the absence of H3K4me3.
• H3K4me3 is essential for INTS11 recruitment, facilitating paused RNAPII eviction and elongation.

Conclusions:

• H3K4me3 plays a critical role in transcriptional pause-release and elongation.
• The primary function of H3K4me3 is to promote transcriptional output by facilitating elongation, rather than initiating transcription.