Histones H3/H4 form a tight complex with the inner nuclear membrane protein LBR and heterochromatin protein 1

We have recently shown that heterochromatin protein 1 (HP1) interacts with the nuclear envelope in an acetylation-dependent manner. Using purified com ponents and in vitro assays, we now demonstrate that HP1 forms a quaternary complex with the inner nuclear membrane protein LBR and a sub-set of core histones. This complex involves histone H3/H4 oligomers, which mediate bind ing of LBR to HP1 and crosslink these two proteins that do not interact dir ectly with each other. Consistent with previous observations, HP1 and LBR b inding to core histones is strongly inhibited when H3/H4 are modified by re combinant CREB-binding protein, revealing a new mechanism for anchoring dom ains of under-acetylated chromatin to the inner nuclear membrane.