Nucleosome sliding by Chd1 does not require rigid coupling between DNA-binding and ATPase domains

Area of Science:

• Molecular Biology
• Epigenetics
• Chromatin Dynamics

Background:

• Chromatin remodellers are ATP-dependent motor proteins essential for nucleosome repositioning.
• The role of the DNA-binding domain (DBD) in Chd1 and Iswi-type remodellers' nucleosome mobilization remains unclear.
• Understanding these mechanisms is crucial for comprehending gene regulation and DNA accessibility.

Purpose of the Study:

• To elucidate the physical mechanism by which the DNA-binding domain (DBD) contributes to nucleosome remodelling.
• To investigate the role of tethering versus pulling in Chd1-mediated nucleosome sliding.
• To determine how linker length and flexibility affect the interaction between the DBD and the ATPase motor.

Main Methods:

• Biochemical assays to measure nucleosome sliding activity.
• In vitro reconstitution of chromatin remodellers with varying linker lengths and flexibility.
• Analysis of the physical contribution of the DNA-binding domain (DBD) to motor protein function.

Main Results:

• The Chd1 DNA-binding domain (DBD) primarily functions by tethering the remodeller to nucleosome substrates.
• Nucleosome sliding activity was robust and largely unaffected by modifications to the linker connecting the DBD and ATPase motor.
• Evidence suggests the ATPase motor does not actively pull DNA onto the nucleosome via the DBD.

Conclusions:

• The Chd1 DBD's role in nucleosome mobilization is primarily through stable tethering to the nucleosome.
• This tethering mechanism facilitates efficient nucleosome sliding by the ATPase motor.
• The findings provide new insights into the mechanics of chromatin remodelling and DNA-protein interactions.