Ribosome hibernation factor; regulates ribosome homeostasis by coupling ribosome biosynthesis and degradation in response to nutrient availability; has nucleolar role promoting ribosome biogenesis during exponential growth, distinct from cytosolic role during nutrient starvation when it forms dormant 80S ribosomes protecting them from proteasomal degradation; perturbs association of Yef3p with ribosomes; binds G4 quadruplex and purine motif triplex nucleic acid; helps maintain telomere structure