Contributions of linker histones and histone H3 to chromatin structure: scanning force microscopy studies on trypsinized fibers. |
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| Authors: | S H Leuba C Bustamante J Zlatanova and K van Holde |
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| Affiliation: | *Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229 USA;#Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1229 USA;§Howard Hughes Medical Institute, University of Oregon, Eugene, Oregon 97403-1229 USA;¶Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305 USA;||Institute of Genetics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria |
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| Abstract: | Little is known about the mechanisms that organize linear arrays of nucleosomes into the three-dimensional structures of extended and condensed chromatin fibers. We have earlier defined, from scanning force microscopy (SFM) and mathematical modeling, a set of simple structural determinants of extended fiber morphology, the critical parameters being the entry-exit angle between consecutive linkers and linker length. Here we study the contributions of the structural domains of the linker histones (LHs) and of the N-terminus of histone H3 to extended fiber morphology by SFM imaging of progressively trypsinized chromatin fibers. We find that cleavage of LH tails is associated with a lengthening of the internucleosomal center-to-center distance, and that the somewhat later cleavage of the N-terminus of histone H3 is associated with a flattening of the fiber. The persistence of the "zigzag" fiber morphology, even at the latest stages of trypsin digestion, can be attributed to the retention of the globular domain of LH in the fiber. |
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