Methylation-Controlled J Protein
MCJ is a member of the DNAJ family of co-chaperone proteins, whose expression is controlled by methylation of its associated CpG island. Reduced MCJ expression increases resistance to several commonly used cancer therapeutics by inducing expression of the ABCB1 drug-transport pump.
The MCJ gene maps at 13q14.1 and codes for a protein of 150 amino acids and 16–17 kDa. MCJ contains a highly conserved 70 amino acid DNAJ domain (or J-domain) located at the C terminus. J-domain proteins interact with the heat shock protein 70 (Hsp70) family of chaperone proteins and act as co-chaperones recruiting Hsp70 members to specific substrate proteins. MCJ has been shown to be a type II transmembrane protein localized in the Golgi network, with a cytoplasmic N terminus and a C terminus lying within the Golgi lumen.