Nucl. Acids Res.-2012-Lim-3316-28.pdf (6.8 MB)
Download fileGene silencing H-NS paralogue StpA forms a rigid protein filament along DNA that blocks DNA accessibility
journal contribution
posted on 2013-11-07, 00:00 authored by Ci Ji Lim, Yixun R. Whang, Linda J. Kenney, Jie YanNucleoid-associated proteins are bacterial proteins
that are responsible for chromosomal DNA compaction
and global gene regulation. One such protein is
Escherichia coli Histone-like nucleoid structuring
protein (H-NS) which functions as a global gene
silencer. Whereas the DNA-binding mechanism of
H-NS is well-characterized, its paralogue, StpA
which is also able to silence genes is less understood.
Here we show that StpA is similar to H-NS
in that it is able to form a rigid filament along DNA. In
contrast to H-NS, the StpA filament interacts with a
naked DNA segment to cause DNA bridging which
results in simultaneous stiffening and bridging of
DNA. DNA accessibility is effectively blocked after
the formation of StpA filament on DNA, suggesting
rigid filament formation is the important step in
promoting gene silencing. We also show that
>1mM magnesium promotes higher order DNA
condensation, suggesting StpA may also play a
role in chromosomal DNA packaging.