G4 quadruplex nucleic acid binding proteins in yeast

G4 quadruplex nucleic acids are four-stranded right-handed helices stabilized by a guanine base quartet hydrogen bonding and stacking arrangement. This structure has been known in vitro for twenty years, however, despite tantalizing evidence, in vivo functions for G4 nucleic acids have not yet been assigned. To identify possible biological roles for these structures, I have analyzed two proteins in yeast, G4p1 and G4p2, which possess G4 nucleic acid binding properties.; G4p1 is a complex containing two identical 42 kDa polypeptide subunits of unknown cellular function. It may interact with the cytoplasmic glutamyl-tRNA synthetase, as this enzyme copurifies extensively. G4p2 is a 30 kDa cytoplasmically localized polypeptide with G4 nucleic acid binding characteristics very similar to G4p1, and may associate with ribosomes. Thus these activities are perhaps functionally linked, and may both participate in some way in the translation process.; G4p2 has been isolated by others as a component of the Pkc1 signal transduction pathway. I speculate that these G4 nucleic acid binding activities are regulatory proteins responding to signals tranduced by protein kinases, and may regulate translation. Nucleic acid components of the translation apparatus may contain G4 domains which permit these proteins to execute their function.