DSIF modulates RNA polymerase II occupancy according to template G + C content

Area of Science:

• Molecular Biology
• Gene Regulation
• Chromatin Structure

Background:

• The DSIF complex, composed of Supt4h and Supt5h, is essential for transcription elongation by RNA polymerase II (RNAPII).
• Previous studies suggest DSIF plays a role in managing RNAPII transit through repetitive DNA sequences.
• Allele-specific expression changes upon DSIF component reduction hint at sequence-dependent roles.

Purpose of the Study:

• To identify genome-wide sequence features influencing RNAPII dependence on DSIF in human cells.
• To investigate the impact of Supt4h loss on DNA template occupancy and gene expression.
• To understand how G+C content affects DSIF's role in transcription.

Main Methods:

• Ultra-deep ChIP-seq analysis to map RNAPII and DSIF binding sites genome-wide.
• RNA-seq to quantify transcript production following Supt4h depletion.
• Bioinformatic analysis correlating DSIF dependence with DNA sequence composition.

Main Results:

• RNAPII dependence on Supt4h varies significantly with DNA G+C content.
• DSIF knockdown effects were most pronounced in G+C-rich regions, especially within long genes.
• Loss of Supt4h impacted transcription most in G+C-rich sequences, with minimal effects in G+C-poor regions.
• Similar G+C content-dependent effects were observed for Supt5h in mouse cells.

Conclusions:

• DNA G+C content is a key determinant of RNAPII dependence on the DSIF complex.
• Supt4h and Supt5h's roles in transcription are modulated by the local DNA sequence composition.
• G+C content may influence the selective impact of DSIF knockdown on genes with repeat expansions.