Figure 2

Structure of HP1 proteins and the genes encoding them. (a) The conserved genomic structure of HP1-encoding genes from Drosophila to humans. Each gene is made up of five exons separated by four introns. The start (ATG) and stop codons are indicated. The exons encoding the chromodomain and the chromoshadow domain are indicated by brackets and arrows. Asterisks mark where murine Cbx3 (encoding HP1γ) differs from the arrangement shown: the start codon is in exon 3 and the chromodomain is encoded by exons 3 and 4 of this gene. (b) The conserved linear structure of HP1 proteins. N, amino terminus; C, carboxy terminus. (c) The overall three-dimensional structures of the chromodomain and chromoshadow domain of murine HP1β. Coordinates were downloaded from the Protein Data Bank (PDB) structural database and modeled using the Insight II program from Accelrys [78].