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Four differently chromatin‐associated maize HMG domain proteins modulate DNA structure and act as architectural elements in nucleoprotein complexes
Authors:Christoph Ritt,Rudi Grimm,Silvia Ferná  ndez,Juan C. Alonso,Klaus D. Grasser
Affiliation:;1Institut für Biologie III, Albert‐Ludwigs‐Universität Freiburg, Schänzlestr. 1, D‐79104 Freiburg, Germany,,;2Hewlett Packard GmbH, Hewlett Packardstr. 8, D‐76337 Waldbronn, Germany, and,;3Centro Nacional de Biotecnología, CSIC, Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
Abstract:In contrast to other eukaryotes which usually express two closely related HMG1-like proteins, plant cells have multiple relatively variable proteins of this type. A systematic analysis of the DNA-binding properties of four chromosomal HMG domain proteins from maize revealed that they bind linear DNA with similar affinity. HMGa, HMGc1/2 and HMGd specifically recognise diverse DNA structures such as DNA mini-circles and supercoiled DNA. They induce DNA-bending, and constrain negative superhelical turns in DNA. In the presence of DNA, the HMG domain proteins can self-associate, whereas they are monomeric in solution. The maize HMG1-like proteins have the ability to facilitate the formation of nucleoprotein structures to different extents, since they can efficiently replace a bacterial chromatin-associated protein required for the site-specific β-mediated recombination. A variable function of the HMG1-like proteins is indicated by their differential association with maize chromatin, as judged by their ‘extractability’ from chromatin with spermine and ethidium bromide. Collectively, these findings suggest that the various plant chromosomal HMG domain proteins could be adapted to act in different nucleoprotein structures in vivo.
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