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Vol. 18, Issue 10, 4013-4023, October 2007

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Expansion of Chromosome Territories with Chromatin Decompaction in BAF53-depleted Interphase Cells

Kiwon Lee^*, Mi Jin Kang^*, Su Jin Kwon^*, Yunhee Kim Kwon, Ki Woo Kim, Jae-Hwan Lim, and Hyockman Kwon^*

*Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Yongin 449-791, Korea; Department of Biology, Kyunghee University, Seoul 130-701, Korea; National Instrumentation Center for Environmental Management, Seoul National University, Seoul 151-921, Korea; and Department of Biology, Andong National University, Andong 760-749, Korea

Submitted May 11, 2007; Revised July 10, 2007; Accepted July 13, 2007
Monitoring Editor: Wendy Bickmore

Chromosomes are compartmentalized into discrete chromosome territories during interphase in mammalian cells. A chromosome territory is generated by the tendency of chromatin to occupy the smallest shell volume, which is determined by the polymeric properties and interactions of the internal meshwork of the chromatin fiber. Here, we show that BAF53 knockdown by small interfering RNA interference led to the expansion of chromosome territories. This was accompanied by a reduction in chromatin compaction, an increase in the micrococcal nuclease sensitivity of the chromatin, and an alteration in H3-K9 and H3-K79 dimethylation. Interestingly, the BAF53 knockdown cells suffer a cell cycle defect. Despite the significant irregularity and decompaction of the polynucleosomes isolated from the BAF53 knockdown cells, the chromatin loading of H1 and core histones remained unaltered, as did the nucleosome spacing. The histone hyperacetylation and down-regulation of BRG-1, mBrm, and Tip49, the catalytic components of the SWI/SNF complex and the TIP60 complex, respectively, did not expand chromosome territories. These results indicate that BAF53 contributes to the polymeric properties and/or the internal meshwork interactions of the chromatin fiber probably via a novel mechanism.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Hyockman Kwon (hmkwon{at}hufs.ac.kr)

Abbreviations used: CT, chromosome territory; HAT, histone acetyl transferase; FISH, Fluorescence in situ hybridization; MNase, micrococcal nuclease; FACS, fluorescence-activated cell sorting.