Genome-wide chromatin remodeling modulates the Alu heat shock response

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• Heat shock response involves transient expression of heat shock proteins.
• Repetitive elements like Alu, alpha satellite, and LINE1 constitute a significant portion of the genome.
• Chromatin structure plays a crucial role in gene regulation.

Purpose of the Study:

• To investigate the effect of heat shock on Alu RNA levels and chromatin accessibility.
• To determine if heat shock induces genome-wide chromatin remodeling.
• To explore the role of chromatin dynamics in the regulation of repetitive elements.

Main Methods:

• Hela cells were subjected to heat shock and recovery.
• Alu RNA levels were measured.
• Chromatin accessibility to restriction enzymes was assessed for Alu, alpha satellite, and LINE1 sequences.
• Nucleosome positioning was inferred from accessibility data.

Main Results:

• Heat shock recovery led to a transient increase in Alu RNA levels, paralleling heat shock protein mRNA expression.
• Chromatin accessibility to restriction enzymes increased transiently for Alu, alpha satellite, and LINE1 sequences.
• Heat shock induced genome-wide chromatin remodeling independent of transcription.
• Increased accessibility suggested nucleosome position scrambling rather than linker lengthening.

Conclusions:

• Heat shock triggers a stress response involving transient Alu RNA upregulation and significant chromatin remodeling.
• Chromatin opening and re-closing appear to regulate the Alu stress response.
• Genome-wide chromatin remodeling during heat shock is independent of transcriptional changes.
• Chromatin structure and dynamics may explain key features of SINE regulation, including their dispersion and high copy number.