Biophysical characterization of the association of histones with single-stranded DNA

Biochim Biophys Acta Gen Subj. 2017 Nov;1861(11 Pt A):2739-2749. doi: 10.1016/j.bbagen.2017.07.018. Epub 2017 Jul 27.

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.

Keywords: Electrophoresis; Force spectroscopy; Histones; Magnetic tweezers; Nucleosome; Single-stranded DNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biophysical Phenomena*
  • Cell Nucleus / chemistry
  • Cell Nucleus / genetics
  • Chromatin / chemistry*
  • Chromatin / genetics
  • DNA Replication / genetics
  • DNA, Single-Stranded / chemistry*
  • DNA, Single-Stranded / genetics
  • Histones / chemistry*
  • Histones / genetics
  • Nucleosomes / chemistry
  • Nucleosomes / genetics
  • Osmolar Concentration

Substances

  • Chromatin
  • DNA, Single-Stranded
  • Histones
  • Nucleosomes