RNA Polymerase II coordinates histone deacetylation at active promoters

Area of Science:

• Molecular Biology
• Epigenetics
• Chromatin Biology

Background:

• Nucleosomes at active promoters possess unique histone modifications and variants.
• These chromatin features are believed to establish and sustain a permissive environment for transcription.
• Conflicting findings exist regarding the dependence of these histone modifications on active transcription.

Purpose of the Study:

• To investigate the role of transcription initiation in establishing and maintaining specific histone modifications at active promoters.
• To determine if histone modifications at transcription start sites (TSSs) and enhancers are dependent on ongoing transcription.

Main Methods:

• Utilized triptolide, a transcription inhibitor, to block transcription initiation and induce RNA Polymerase II degradation.
• Examined the impact of inhibiting transcription initiation on histone acetylation and H2AZ incorporation at TSSs and enhancers.

Main Results:

• Transcription initiation was found to be dispensable for both *de novo* and steady-state histone acetylation at TSSs and enhancers.
• Blocking transcription initiation led to increased levels of histone acetylation and H2AZ incorporation at active TSSs under steady-state conditions.
• These findings indicate that transcription actively limits the maintenance of certain histone marks.

Conclusions:

• The deposition of specific histone modifications at TSSs is independent of transcription.
• Active transcription plays a role in limiting the accumulation or maintenance of these histone modifications at active TSSs.