Large Subunit GTPase 1 Homolog (LSG1)

LSG1 is a member of the novel Ylqf-related GTPase (YRG) family. LSG1 shuttles between nuclear Cajal bodies and the endoplasmic reticulum and is required for cell viability. Yeast Lsg1 is involved in ribosome biogenesis.

The deduced 658-amino acid protein contains an N-terminal coiled-coil domain, a central MMR/HSR1 GTPase domain, and nuclear localization signal. In LSG1, the 4 conserved elements of the GTPase domain G1, G2, G3, and G4 are circularly permutated and reorganized, as G4 is followed by G1, G2, and G3. Immunohistochemistry localized LSG1 to the endoplasmic reticulum in HeLa cells with 10% of cells showing localization to discrete nuclear structures identified as Cajal bodies. LSG1 undergoes nucleocytoplasmic trafficking via a CRM1 (XPO1)-dependent export mechanism.