Nematodes expressing a SBP-1TGFP fusion protein driven by the
sbp-1 promoter exhibit strong nuclear fluorescence in the intestinal cells of fed animals, whereas fasted animals show markedly reduced nuclear SBP-1TGFP levels, consistent with previously published results in mammals. In contrast, nuclear SBP-1TGFP expression remains high in fasted nematodes carrying a deletion in
sir-2.1, or in animals treated with the sirtuin inhibitors nicotinamide and sirtinol. Transcript levels of
sbp-1 are only very modestly altered by feeding/fasting or loss of
sir-2.1, suggesting that SIR-2.1 mediates fasting-dependent regulation of SBP-1 protein levels by a post-transcriptional mechanism.