A human RNA polymerase II complex containing factors that modify chromatin structure

Area of Science:

• Molecular Biology
• Gene Transcription
• Chromatin Dynamics

Background:

• RNA polymerase II (Pol II) is central to gene transcription.
• Chromatin remodeling and histone acetylation are key epigenetic modifications regulating gene expression.
• The precise composition and function of large Pol II-associated complexes are still being elucidated.

Purpose of the Study:

• To isolate and characterize a novel human RNA polymerase II complex.
• To investigate the enzymatic activities associated with this complex.
• To determine the interactions between RNA polymerase II and associated proteins.

Main Methods:

• Purification of the RNA polymerase II complex using conventional and affinity chromatography (anti-CDK8 antibodies).
• Biochemical assays to assess chromatin structure remodeling and histone acetyltransferase activity.
• Protein interaction studies (e.g., co-immunoprecipitation) to map protein-protein interactions.

Main Results:

• Isolation of a human RNA polymerase II complex containing Srb proteins, Swi-Snf, CBP, and PCAF, but lacking general transcription factors.
• Demonstration of chromatin structure remodeling and histone acetyltransferase activities within the purified complex.
• Direct interactions observed between RNA polymerase II and histone acetyltransferases p300 and PCAF.
• Differential interaction of p300 with nonphosphorylated Pol II (initiation) and PCAF with phosphorylated Pol II (elongation).

Conclusions:

• A novel human RNA polymerase II complex possesses both chromatin remodeling and histone acetyltransferase functions.
• This complex integrates distinct enzymatic activities crucial for regulating transcription initiation and elongation.
• The findings reveal a sophisticated mechanism for coordinated gene expression control mediated by RNA polymerase II-associated factors.