At the nuclear envelope in higher eukaryotic cells, the nuclear lamina and the 
heterochromatin are adjacent to the inner nuclear membrane, and their attachment 
is presumably mediated by integral membrane proteins. In a yeast two-hybrid 
screen, the nucleoplasmic domain of lamin B receptor (LBR), an integral protein 
of the inner nuclear membrane, associated with two human polypeptides homologous 
to Drosophila HP1, a heterochromatin protein involved in position-effect 
variegation. LBR fusion proteins bound to HP1 proteins synthesized by in vitro 
translation and present in cell lysates. Antibodies against LBR also 
co-immunoprecipitated HP1 proteins from cell extracts. LBR can interact with 
chromodomain proteins that are highly conserved in eukaryotic species and may 
function in the attachment of heterochromatin to the inner nuclear membrane in 
cells.