Germ Cell Associated Protein 1 (GSG1)

GSG1, a TPAP interaction partner protein using yeast two-hybrid and coimmunoprecipitation assays. Subcellular fractionation analysis showed that GSG1 is exclusively localized in the endoplasmic reticulum (ER) of mouse testis where TPAP is also present. In NIH3T3 cells cotransfected with TPAP and GSG1, both proteins colocalize in the ER. Moreover, expression of GSG1 stimulates TPAP targeting to the ER, suggesting that interactions between the two proteins lead to the redistribution of TPAP from the cytosol to the ER. Gsg1 (germ cell associated 1) was not expressed in telogen phase but was markedly up-regulated during the depilation-induced hair cycle. Such change in Gsg1 expression has not previously been reported, and this may provide a useful seed for further evaluation of the event occurring during the hair cycling.