The Gene and Pseudogenes of Cbx3/mHPlγ

The HP1 class of chromobox (Cbx) genes encode an evolutionarily conserved family of proteins involved in the packaging of chromosomal domains into a repressive heterochromatic state. The murine Cbx5, Cbxl and Cbx3 genes encode the three mouse HP1 proteins, mHPlot, -β and -γ respectively. Here, we report the cloning of the mouse Cbx31 HPlγ gene and the chromosomal localisation of Cbx3 and three Cfo3-related pseudogenes. The Cbx3 structural gene is located on mouse Chromosome 6, close to the Hoxa cluster. Two Cbx3 processed pseudogenes are separated by just 300 bp and are arranged in a head-to-tail configuration on Chromosome 13 while a third pseu-dogene is found on mouse Chromosome 4. The genomic intron-exon arrangement of Cbx3 is different from the conserved organisation of three other mammalian HP1 genes, Cbxl (mHPip), CBX3 (hHPly), and Cbx5 (mHPla) in that Cbx3 lacks an intron that is present in the others.