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Mol. Cell. Biol., 03 1995, 1602-1612, Vol 15, No. 3
K Kitagawa, H Masumoto, M Ikeda and T Okazaki
We previously reported that centromere protein B (CENP-B) forms a stable
complex (designated complex A) containing two alphoid DNAs in vitro.
Domains in the CENP-B polypeptide involved in the formation of complex A
were determined in the present study with truncated derivatives expressed
in Escherichia coli and in rabbit reticulocyte lysates. It was revealed by
gel mobility shift analyses that polypeptides containing the NH2-terminal
DNA-binding domain bind a DNA molecule as a monomer, while dimerizing at a
novel hydrophobic domain in the COOH-terminal region of 59 amino acid
residues. This polypeptide dimerization activity at the COOH-terminal
region was also confirmed with the two-hybrid system in Saccharomyces
cerevisiae cells. The results thus proved that CENP-B polypeptides form a
homodimer at the COOH-terminal hydrophobic domain, each binding a DNA
strand at their NH2-terminal domains. The dimerization and DNA-binding
domains fall into two of the three completely conserved sequences found in
human and mouse CENP-B, and complex A-forming activity was also detected in
nuclear extracts of mouse cells. Metaphase-specific phosphorylation of
CENP-B was also detected, but this had no effect on its complex A- forming
activity. On the basis of the present results, we propose that CENP-B plays
an important role in the assembly of specific centromere structures by
forming unique DNA-protein complexes at the sites of CENP- B boxes on the
centromeric repetitive DNA both in interphase nuclei and on mitotic
chromosomes.
Copyright © 1995, American Society for Microbiology
Analysis of protein-DNA and protein-protein interactions of centromere protein B (CENP-B) and properties of the DNA-CENP-B complex in the cell cycle
Department of Molecular Biology, School of Science, Nagoya University, Japan.
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