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  • Title: Biophysical characterization of the association of histones with single-stranded DNA.
    Author: Wang Y, van Merwyk L, Tönsing K, Walhorn V, Anselmetti D, Fernàndez-Busquets X.
    Journal: Biochim Biophys Acta Gen Subj; 2017 Nov; 1861(11 Pt A):2739-2749. PubMed ID: 28756274.
    Abstract:
    BACKGROUND: Despite the profound current knowledge of the architecture and dynamics of nucleosomes, little is known about the structures generated by the interaction of histones with single-stranded DNA (ssDNA), which is widely present during replication and transcription. METHODS: Non-denaturing gel electrophoresis, transmission electron microscopy, atomic force microscopy, magnetic tweezers. RESULTS: Histones have a high affinity for ssDNA in 0.15M NaCl ionic strength, with an apparent binding constant similar to that calculated for their association with double-stranded DNA (dsDNA). The length of DNA (number of nucleotides in ssDNA or base pairs in dsDNA) associated with a fixed core histone mass is the same for both ssDNA and dsDNA. Although histone-ssDNA complexes show a high tendency to aggregate, nucleosome-like structures are formed at physiological salt concentrations. Core histones are able to protect ssDNA from digestion by micrococcal nuclease, and a shortening of ssDNA occurs upon its interaction with histones. The purified (+) strand of a cloned DNA fragment of nucleosomal origin has a higher affinity for histones than the purified complementary (-) strand. CONCLUSIONS: At physiological ionic strength histones have high affinity for ssDNA, possibly associating with it into nucleosome-like structures. GENERAL SIGNIFICANCE: In the cell nucleus histones may spontaneously interact with ssDNA to facilitate their participation in the replication and transcription of chromatin.
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