H-NS forms a superhelical protein scaffold for DNA condensation

Abstract

The histone-like nucleoid structuring (H-NS) protein plays a fundamental role in DNA condensation and is a key regulator of enterobacterial gene expression in response to changes in osmolarity, pH, and temperature. The protein is capable of high-order self-association via interactions of its oligomerization domain. Using crystallography, we have solved the structure of this complete domain in an oligomerized state. The observed superhelical structure establishes a mechanism for the self-association of H-NS via both an N-terminal antiparallel coiled-coil and a second, hitherto unidentified, helix-turn-helix dimerization interface at the C-terminal end of the oligomerization domain. The helical scaffold suggests the formation of a H-NS:plectonemic DNA nucleoprotein complex that is capable of explaining published biophysical and functional data, and establishes a unifying structural basis for coordinating the DNA packaging and transcription repression functions of H-NS.chromatin | DNA binding | nucleoid | supercoil | transcriptional regulation

Ler of pathogenic Escherichia coli forms toroidal protein–DNA complexes

“…3g). These data were consistent with the observed concentration dependence of self-association of the truncated N-terminal H-NS 1-83 protein (Arold et al, 2010;Leonard et al, 2009). Oligomerization of Ler was impaired in a chimeric protein containing an 11 aa portion of the H-NS linker inserted into the central region of the Ler molecule (Fig.…”

“…Although Ler, like H-NS, forms dimers and oligomers in solution, it is currently unknown whether Ler forms a coiled-coil structure similar to that of H-NS. More recent structural information, in addition to previously published reports, strongly suggests that H-NS forms anti-parallel dimers in solution (Arold et al, 2010;Bloch et al, 2003), and our preliminary structural data suggest that Ler also forms dimers in the same orientation, mediated by the N-terminal coiled-coil motif (data not shown).…”

“…Previous analyses have demonstrated that Ler is predicted to have two a-helices in the N-terminal region, whereas H-NS possesses three ahelices between amino acid positions 1 and 70 (Arold et al, 2010;Bloch et al, 2003;Esposito et al, 2002;Mellies et al, 2008). The amino acid substitution I26R within the predicted coiled-coil domain of Ler eliminates Ler binding to regulatory DNA and the ability to increase transcriptional activity from a LEE2-lacZ fusion in vivo .…”

“…The H-NS N-terminal domain contains three a-helices between amino acid positions 1 and 70 and dimerizes as a coiledcoil, as determined by NMR structural analysis (Arold et al, 2010;Bloch et al, 2003;Esposito et al, 2002). The Ler Nterminal domain contains only two predicted a-helices (Mellies et al, 2008) and a shorter coiled-coil motif than that of H-NS (Fig.…”

Structural Insights into Nonspecific Binding of DNA by TrmBL2, an Archaeal Chromatin Protein

“…A structural comparison of the two reveals that H-NS also contains the C-terminal wHTH DNA binding domain [34] and an N-terminal domain that has been proposed to facilitate oligomerization [35]. Since the N-and C-terminal structures of H-NS have been solved separately, the orientation of the wHTH domain with respect to the C-terminal oligomerization domain is not known.…”