Chromobox Homolog 7 (CBX7)

CBX7 contains an N-terminal chromodomain and a C-terminal Pc box. Phylogenetic analysis showed that CBX7 shares highest similarity with CBX2, CBX4, CBX6, and CBX8. CBX7 mRNA was highly expressed in brain, heart, kidney, and skeletal muscle, and weakly expressed in peripheral blood leukocytes.Expression of either mouse or human CBX7 could extend the cellular life span of mouse embryonic fibroblasts and human cells by downregulating expression of the Ink4a/Arf gene (CDKN2A). Expression of human CBX7 mutants lacking the Pc box or with mutations in critical residues of the chromodomain did not extend the life span of cultured cells. CBX7 interacted with itself and with RING1 in an in vitro pull-down assay, and CBX7 colocalized with RING1 in distinct nuclear foci-like structures termed Pc bodies.