The proto-chromatosome: A fundamental subunit of chromatin?

JOSEFINA OCAMPO; FENG CUI; VICTOR B. ZURKIN; CLARK D J

nucleus

Landes Bioscience

Año: 2016 vol. 7 p. 382 - 387

1949-1034

Eukaryotic DNA is packaged into regularly spaced nucleosomes, resembling beads on a string. Each bead contains »147 bp wrapped around a core histone octamer. Linker histone (H1) binds to the linker DNA to drive chromatin folding. Micrococcal nuclease (MNase) digestion studies reveal 2 mono-nucleosomal intermediates: the core particle (»147 bp) and the chromatosome (»160 bp; a core particle with additional DNA protected by H1). We have recently developed an improved method for mapping nucleosomes, using exonuclease III to remove residual linker (MNase-Exo- seq).1 We discovered 2 new intermediate particles corresponding to core particles with »7 bp of linker protruding from one side (»154 bp) or both sides (»161 bp), which are formed in the absence of H1. We propose that these ?proto-chromatosomes? are stabilised by core histone-DNA contacts in the linker, »7 bp from the nucleosome boundaries. These contacts may determine the topography of the H1 binding site.