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Abstract
The centromere is responsible for accurate chromosome segregation. Mammalian centromeres
are specified epigenetically, with all active centromeres containing centromere-specific
chromatin in which CENP-A replaces histone H3 within the nucleosome. The proteins
responsible for assembly of human CENP-A into centromeric nucleosomes during the G1
phase of the cell cycle are shown here to be distinct from the chromatin assembly
factors previously shown to load other histone H3 variants. Here we demonstrate that
prenucleosomal CENP-A is complexed with histone H4, nucleophosmin 1, and HJURP. Recruitment
of new CENP-A into nucleosomes at replicated centromeres is dependent on HJURP. Recognition
by HJURP is mediated through the centromere targeting domain (CATD) of CENP-A, a region
that we demonstrated previously to induce a unique conformational rigidity to both
the subnucleosomal CENP-A heterotetramer and the corresponding assembled nucleosome.
We propose HJURP to be a cell-cycle-regulated CENP-A-specific histone chaperone required
for centromeric chromatin assembly.