CENP-A-containing nucleosomes: easier disassembly versus exclusive centromeric localization.
CENP-A is a histone variant that replaces conventional H3 in nucleosomes of functional centromeres. We report here, from reconstitutions of CENP-A- and H3-containing nucleosomes on linear DNA fragments and the comparison of their electrophoretic mobility, that CENP-A induces some positioning of its own and some unwrapping at the entry-exit relative to canonical nucleosomes on both 5 S DNA and the alpha-satellite sequence on which it is normally loaded. This steady-state unwrapping was quantified to 7(+/-2) bp by nucleosome reconstitutions on a series of DNA minicircles, followed by their relaxation with topoisomerase I. The unwrapping was found to ease nucleosome invasion by exonuclease III, to hinder the binding of a linker histone, and to promote the release of an H2A-H2B dimer by nucleosome assembly protein 1 (NAP-1). The (CENP-A-H4)2 tetramer was also more readily destabilized with heparin than the (H3-H4)2 tetramer, suggesting that CENP-A has evolved to confer its nucleosome a specific ability to disassemble. This dual relative instability is proposed to facilitate the progressive clearance of CENP-A nucleosomes that assemble promiscuously in euchromatin, especially as is seen following CENP-A transient over-expression.
Conde e Silva
Natalia
N
Institut Jacques Monod (UMR CNRS 7592), 2 place Jussieu, 75251 Paris Cédex 05, France.
Black
Ben E
BE
Sivolob
Andrei
A
Filipski
Jan
J
Cleveland
Don W
DW
Prunell
Ariel
A
D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002503:Centromere / Q000378:metabolism*; D000076247:Centromere Protein A; D002645:Chickens; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006493:Heparin / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D009690:Nucleic Acid Conformation; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D016415:Sequence Alignment
D001324:Autoantigens; C000619700:CENPA protein, human; D018797:Cell Cycle Proteins; D000076247:Centromere Protein A; D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D046911:Macromolecular Substances; C533557:NAP1L1 protein, human; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes; D006493:Heparin; D004247:DNA; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III