Protein HU binds specifically to kinked DNA |
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Authors: | Andrea Pontiggia Armando Negri Monica Beltrame Marco E. Bianchi |
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Affiliation: | Istituto Scientifico Ospedale San Raffaele, via Olgettina 60, I-20132 Milano, italy.;Istituto di Fisiologia Veterinaria e Biochimica, Universita'di Milano, via Celoria 10, 1-20133 Milano, Italy.;Dipartimento di Genetica e di Biologia dei Microrganismi, Universita'di Milano, via Celoria 26, i-20133 Milano, Italy. |
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Abstract: | We have purified the main four-way junction DNA-binding protein of Escherichia coli, and have found It to be the well-known HU protein. HU protein recognizes with high-affinity one of the angles present in the junction, a molecule with the shape of an X. Other DNA structures characterized by sharp bends or kinks, like bulged duplex DNAs containing unpaired bases, are also bound. HU protein appears to inhibit cruciform extrusion from supercoiled inverted repeat (palindromic) DNA, either by constraining supercoiling or by trapping a metastable interconversion intermediate. All these properties are analogous to the properties of the mammalian chromatin protein HMG1. We suggest that HU is a prokaryotic HMG1-like protein rather than a histone-like protein. |
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