Researchers have discovered a new mechanism with which DNA is repaired that could lead to further developments in the treatment and prevention of neurodegenerative disorders such as Alzheimer’s disease.
Researchers have discoveredthat a special enzyme – the RNA polymerase II (Pol II) enzyme – can sense these SSBs by “riding” along the DNA coil. Acting almost like a proofreader of a text, when the Pol II enzyme encounters an SSB, it triggers a number of reactions that lead to repair enzymes fixing the damaged area.
“RNA polymerase can ‘crawl’ along the DNA loops nearly as well as on histone-free DNA regions, but when it stops near locations of the DNA breaks, it ‘panics,’ triggering the cascade of reactions to start DNA ‘repairs,'” Prof. Studitsky explains.
For the study, the researchers inserted SSBs into a model DNA system to observe how they would affect the progress of Pol II progressing along the coils. They discovered that this enzyme only stopped upon encountering breaks in the DNA connected to the histones and not in histone-free DNA.
“These observations raise the possibility that nucleosomal structure could affect the process of detection and repair of DNA damages,” the authors write.
Prior to the study, the researchers had thought that DNA repair was only possible in histone-free DNA, as reparation with the previously identified mechanism would require complete unwinding of the DNA coils to make the SSBs accessible.