JMJD6/PSR: ProductsJMJD6 (Jumonji [Japanese for âcruciform/crossâ] domain-containing protein 6; also PTDSR/PSR and Lysyl-hydroxylase JMJD6) is a 47-55 kDa member of the JMJD6 family, cupin superfamily of proteins. It is induced by hypoxia, and expressed in skeletal muscle, macrophages, and possibly endothelial cells. JMJD6 has been reported to demethylate histones, although this is now considered unlikely. It was also initially reported to serve as a phosphatidyl serine receptor, but the data regarding this activity is conflicting. What does seem clear is that JMJD6 acts as a lysyl hydroxylase. In the nucleus, it appears to regulate pre-RNA splicing by hydroxylating various splicing factors such as U2AF65.