Wang, YingMerwyk, Luis VanTönsing, KatjaWalhorn, VolkerAnselmetti, DarioFernàndez Busquets, Xavier2017-09-262018-07-272017-07-270006-3002https://hdl.handle.net/2445/115793BACKGROUND: 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 at physiological salt concentrations, 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. Whereas histone-ssDNA complexes show a high tendency to aggregate in 0.2 M NaCl, at lower ionic strength nucleosome-like structures are formed. 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.29 p.application/pdfengcc-by-nc-nd (c) Elsevier, 2017http://creativecommons.org/licenses/by-nc-nd/3.0/esHistonesCromatinaHistonesChromatineinfo:eu-repo/semantics/article2017-08-30info:eu-repo/semantics/openAccess