- Promoter regions of the human X-linked housekeeping genes PRPS1 and PRPS2 encoding phosphoribosylpyrophosphate synthetase subunit I and II isoforms. Ishizuka, T., Iizasa, T., Taira, M., Ishijima, S., Sonoda, T., Shimada, H., Nagatake, N., Tatibana, M. Biochim. Biophys. Acta (1992)