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Bao, Y., Konesky, K., Park, Y.J., Rosu, S., Dyer, P.N., Rangasamy, D., Tremethick, D.J., Laybourn, P.J., Luger, K. (2004). Nucleosomes containing the histone variant H2A. Bbd organize only 118 base pairs of DNA.  EMBO J. 23(16): 3314--3324.
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Research paper

H2A.Bbd is an unusual histone variant whose sequence is only 48% conserved compared to major H2A. The major sequence differences are in the docking domain that tethers the H2A-H2B dimer to the (H3-H4)(2) tetramer; in addition, the C-terminal tail is absent in H2A.Bbd. We assembled nucleosomes in which H2A is replaced by H2A.Bbd (Bbd-NCP), and found that Bbd-NCP had a more relaxed structure in which only 118+/-2 bp of DNA is protected against digestion with micrococcal nuclease. The absence of fluorescence resonance energy transfer between the ends of the DNA in Bbd-NCP indicates that the distance between the DNA ends is increased significantly. The Bbd docking domain is largely responsible for this behavior, as shown by domain-swap experiments. Bbd-containing nucleosomal arrays repress transcription from a natural promoter, and this repression can be alleviated by transcriptional activators Tax and CREB. The structural properties of Bbd-NCP described here have important implications for the in vivo function of this histone variant and are consistent with its proposed role in transcriptionally active chromatin.

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PMC514500 (PMC) (EuropePMC)
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    EMBO J.
    The EMBO Journal
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