interests = Our current primary interest is the mechanism of sensing oxygen, an environmental factor that is pivotal in the regulation of fruiting and sporulation. We have identified a molecular mechanism that is centered on O2- and alpha-ketoglutarate-dependent prolyl hydroxylation of Skp1, an adaptor in the major SCF class of E3-polyubiquitin ligases. Hydroxylation of Pro-143 enables subsequent glycosylation by a series of 5 glycosyltransferase reactions, whose end effect is to promote assembly of the SCF complex. This is in turn is expected to promote turnover of proteins whose exit are necessary for developmental progression. The Dictyostelium system serves as a useful model for a related mechanism that is shared by a diverse set of unicellular eukaryotes.