Transcription-induced active forces suppress chromatin motion

Area of Science:

• Biophysics
• Molecular Biology
• Genomics

Background:

• Interphase chromosome organization is increasingly understood through experimental techniques.
• Chromatin dynamics, particularly during functional states like transcription, remain less understood.
• Experiments show decreased locus motility during human transcription, counterintuitive to expected chromatin opening.

Purpose of the Study:

• To investigate how active mechanical forces (F) influence chromatin dynamical properties.
• To explain the counterintuitive observation of decreased locus mobility during transcription.

Main Methods:

• Development of a minimal active copolymer model for interphase chromosomes.
• Simulation of locus movements under varying active forces (F).

Main Results:

• Locus movements in gene-rich regions are suppressed at intermediate forces (F) and enhanced at low forces.
• Intermediate forces cause increased bond lengths and a transient disorder-to-order transition, reducing mobility.
• This force-dependent dynamics preserves chromosome organization and may nucleate dynamic networks.

Conclusions:

• The model explains the experimentally observed suppression of chromatin mobility during transcription.
• A transient ordering mechanism in gene-rich regions, driven by mechanical forces, is proposed.
• This mechanism could be crucial for forming dynamic networks involving transcription machinery and chromatin.