Phosphoribosyl Pyrophosphate Synthetase 2 (PRPS2)

PRPS2 encodes a phosphoribosyl pyrophosphate synthetase that plays a central role in the synthesis of purines and pyrimidines. The encoded protein catalyzes the synthesis of 5-phosphoribosyl 1-pyrophosphate from ATP and D-ribose 5-phosphate. Alternate splicing results in multiple transcript variants.

The ZFX gene, which escapes X-inactivation, is bracketed proximally by the POLA gene which, like PRPS2, undergoes inactivation. The A1S9T locus in the proximal short arm and the RPS4X gene in the proximal long arm are other loci that escape inactivation and are interspersed among genes that do undergo X-inactivation. Furthermore, the XIST gene , located at Xq13, is transcribed only from the inactive X chromosome.