grp 17

GADD45G, also known as CR6, is part of the nuclear proteins to interact with various proteins whose transcript levels are raised after stressful growth arrest conditions and treatment with DNA-damaging agents. GADD45G reacts to environmental stresses by mediating activation of the p38 JNK pathway which is mediated through their protein binding and activating MTK1 MEKK4 kinase, which is an upstream activator of both p38 and JNK MAPKs. GADD45G acts as a new-age tumor suppressor however is being frequently inactivated epigenetically in multiple tumors. GADD45G mRNA expression is down-regulated in hepatocellular carcinoma. GADD45G causes cell cycle arrest at G2 M transition when transfected into Hep-G2 cells. GADD45G induction by androgens involves new protein synthesis. Overexpression of GADD45G inhibits cell growth and causes morphological modifications in prostate cell lines thus GADD45G takes part in differentiation induction by androgens.

Hypoxia up-regulated protein 1, also known as 15 kDa oxygen-regulated protein, 17 kDa glucose-regulated protein, ORP-15, GRP-17, and HYOU1, is a member of the heat shock protein 7 family. Seven members from four different heat shock protein (HSP) families were identified including HYOU1 (ORP15), HSPC1 (HSP86), HSPA5 (Bip), HSPD1 (HSP6), and several isoforms of the two testis-specific HSP7 chaperones HSPA2 and HSPA1L. HYOU1 is highly expressed in tissues that contain well-developed endoplasmic reticulum and synthesize large amounts of secretory proteins. It is highly expressed in the liver and pancreas. HYOU1 is also expressed in macrophages within aortic atherosclerotic plaques and in breast cancers. HYOU1 has a pivotal role in cytoprotective cellular mechanisms triggered by oxygen deprivation. It may play a role as a molecular chaperone and participate in protein folding. Suppression of HYOU1 is associated with accelerated apoptosis. It is suggested to have an important cytoprotective role in hypoxia-induced cellular perturbation. This protein is up-regulated in tumors, especially in breast tumors, and thus it is associated with tumor invasiveness.