Crosstalk within a functional INO80 complex dimer regulates nucleosome sliding.

Area of Science:

• Chromatin biology
• Molecular mechanisms of DNA repair
• Nucleosome dynamics

Background:

• Chromatin remodellers, such as ISWI and INO80 complexes, regulate nucleosome spacing on DNA.
• ISWI remodellers utilize H4 histone tails and specific motor domain motifs (AutoN, NegC) to control ATPase activity and DNA sensing.
• INO80 complexes lack H4 tail regulation and AutoN/NegC motifs, suggesting alternative mechanisms for nucleosome spacing.

Purpose of the Study:

• To elucidate the distinct mechanism by which the INO80 complex spaces nucleosomes.
• To investigate the role of cooperativity between INO80 complexes in nucleosome sliding.
• To characterize the function of the Ino80 C-terminal domain (Ino80CTD) in regulating ATPase activity and sliding.

Main Methods:

• Biochemical assays to study nucleosome sliding and ATPase activity.
• Investigating the cooperative binding of Ino80CTD to DNA.
• Analyzing the role of Ino80CTD dimerization in inter-complex crosstalk.

Main Results:

• INO80 complex-mediated nucleosome spacing relies on cooperativity between two complexes simultaneously monitoring DNA length.
• The human Ino80 C-terminal domain (Ino80CTD) binds DNA cooperatively, facilitating crosstalk between INO80 complexes.
• ATPase activity becomes uncoupled from sliding as it reaches completion, regulated by Ino80CTD; a single active ATPase motor suffices for sliding.

Conclusions:

• INO80 complex achieves nucleosome spacing through a cooperative, dual-complex mechanism distinct from ISWI remodellers.
• The Ino80CTD plays a crucial role in regulating the termination of nucleosome sliding by controlling ATPase activity.
• Understanding INO80 complex function provides insights into chromatin dynamics and regulation.