GPN1/XAB1 (DNA Repair & Protein Synthesis)

GPN1 is involved in protein synthesis events. It is expressed ubiquitously with highest expression in testis. It binds to the RNA polymerase II- (Poll II) associated proteins RPAP1-3 and to XPA (a protein involved in DNA repair mechanisms), thereby forming an interface with Poll II. Via this interaction, GPN1 is thought to mediate the involvement of Pol II in both protein complex formation and protein chaperone/ scaffolding activities. In addition, GPN1 interacts with components of the integrator and molecular chaperone complexes, further implicating GPN1 in protein assembly. GPN1 contains a cluster of acidic amino acids in its C-terminal region and a series of sequences similar to those found in GTP-binding proteins in its N-terminal region, suggesting that GPN1 has possible GTPase activity.