Right-handed DNA Supercoiling by an Octameric Form of Histone-like Protein HU

In bacteria, the contribution of global nucleoid organization in determining cellular transcription programs is unclear. Using a mutant form of the most abundant nucleoid-associated protein HU, HUalpha(E38K,V42L), we previously showed that nucleoid remodeling by the mutant protein re-organizes the global transcription pattern. Here, we demonstrate that, unlike the dimeric wild-type HU, HUalpha(E38K,V42L) is an octamer and wraps DNA around its surface. The formation of wrapped nucleoprotein complexes by HUalpha(E38K,V42L) leads to a high degree of DNA condensation. The DNA wrapping is right-handed, which restrains positive supercoils. In vivo, HUalpha(E38K,V42L) shows altered association and distribution patterns with the genetic loci whose transcription are differentially affected in the mutant strain.