SSB, a dynamic protector of single-stranded DNA
Whenever the double helix of
DNA unravels, exposing each strand to the harsh environment of the
cell, SSB is usually first on the scene. Although DNA unwinding is
necessary for replication or recombination, it is normally a
transient process. Exposed single-stranded DNA (ssDNA) can be damaged
or degraded by enzymes in the cell. Damaged DNA may also come
unwound, and ssDNA can bond to itself, forming hairpin loops and
other problematic structures.
"If you have lots of single-stranded DNA in the cell, basically it's a sign of trouble," said Taekjip Ha who led the study. "SSB needs to come and bind to it to protect it from degradation and to control what kind of proteins have access to the single-stranded DNA." Although other proteins are known to travel along double-stranded DNA, this is the first study to find a protein that migrates back and forth randomly on _single-stranded_ DNA.
DNA-binding Protein Is Dynamic, Critical To DNA Repair. /ScienceDaily/. Retrieved November 2, 2009, on
The work has been published in Nature:
SSB protein diffusion on single-stranded DNA stimulates RecA filament formation.
Roy R, Kozlov AG, Lohman TM, Ha T
Nature. 2009 Oct 22;461(7267):1092-7. Epub 2009 Oct 11.