At the nuclear envelope, the nuclear lamina and heterochromatin are adjacent to the inner nuclear membrane. CBX3 binds DNA and is a component of heterochromatin. CBX3 also can bind lamin B receptor, an integral membrane protein found in the inner nuclear membrane. The dual binding functions of CBX3 may explain the association of heterochromatin with the inner nuclear membrane.At the nuclear envelope, the nuclear lamina and heterochromatin are adjacent to the inner nuclear membrane. The protein encoded by this gene binds DNA and is a component of heterochromatin. This protein also can bind lamin B receptor, an integral membrane protein found in the inner nuclear membrane. The dual binding functions of the encoded protein may explain the association of heterochromatin with the inner nuclear membrane. Two transcript variants encoding the same protein but differing in the 5' UTR, have been found for this gene.