Chromatin remodeling by RSC involves ATP-dependent DNA translocation.

Area of Science:

• Molecular Biology
• Chromatin Biology
• Biochemistry

Background:

• Chromatin remodeling complexes are essential for regulating gene accessibility.
• These complexes utilize ATP hydrolysis to alter histone-DNA interactions and nucleosome mobility.
• Understanding the precise mechanism of nucleosome remodeling is key to deciphering gene regulation.

Purpose of the Study:

• To investigate the mechanistic basis of nucleosome remodeling by the RSC complex.
• To determine if RSC and its Sth1 subunit possess DNA translocase activity.
• To elucidate the roles of DNA translocation and twist in the remodeling process.

Main Methods:

• Triple-helix strand-displacement assays were employed to study DNA interactions.
• DNA length-dependent ATPase assays were used to measure enzyme activity.
• DNA-minicircle ATPase assays provided further insights into translocation.
• Nucleosomes with precise nicks were utilized to decouple twist and translocation.

Main Results:

• The RSC complex and its isolated ATPase subunit, Sth1, were identified as DNA translocases.
• RSC/Sth1 ATPase activity is stimulated by single-stranded DNA, indicating strand tracking.
• Isolated Sth1 demonstrated nucleosome remodeling capability.
• Nucleosomes with nicks were remodeled less efficiently than intact nucleosomes, highlighting the importance of twist.

Conclusions:

• RSC and Sth1 function as DNA translocases, moving DNA segments across the histone octamer.
• Nucleosome remodeling is achieved through a combination of DNA translocation and DNA twist.
• This mechanism provides a wave-like propagation of DNA alteration around the nucleosome.