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The 180 bp family of tandem repetitive sequences, which constitutes the major centromeric satellite in Arabidopsis thaliana, is thought to play important roles in kinetochore assembly. To assess the centromere activities of the 180 bp repeats, we performed indirect fluorescence immunolabeling with antibodies against phosphorylated histone H3 at Serl0, HTR12 (Arabidopsis centromeric histone H3 variant) and AtCENP-C (Arabidopsis CENP-C homologue) for the A. thaliana cell cultures. The immunosignals from all three antibodies appeared on all sites of the 180 bp,repeats detected by fluorescence in situ hybridization. However, some of the 180 bp repeat clusters, particularly those that were long or stretched at interphase, were not fully covered with the signals from anti-HTR12 or AtCENP-C. Chromatin fiber immunolabeling clearly revealed that the centromeric proteins examined in this study, localize only at the knobs on the extended chromatin fibers, which form a limited part of the 180 bp clusters. Furthermore, outer HTR12 and inner phosphohistone H3 (Ser1O) localization at the kinetochores of metaphase chromosomes suggests that two kinds of histone H3 (a centromere variant and a phosphorylated form) might be linked to different roles in centromere functionality; the former for spindle-fiber attachment, and the latter for chromatid cohesion.
180 bp repeat
Digital Object Identifer:10.1242/jcs.01144
Published with permission from the copyright holder.This is the institute's copy, as published in Journal of Cell Science, 15 June 2004, Volume 117, Issue 14, Pages 2963-2970.
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Copyright © 2004 The Company of Biologists Ltd. All rights reserved.
Journal of Cell Science
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