growth factor stimulation, and ROS is known to activate Src and Jak family kinases (11, 23, 24). Thus, Rac1 may both localize STAT3 to kinase complexes and contribute to the activation of the kinases themselves. References and Notes 1. J. E. Darnell Jr., Science 277, 1630 (1997). 2. J. N. Ihle et al., Trends Biochem. Sci. 19, 222 (1994). 3. K. Shuai et al., Cell 76, 821 (1994). 4. T. E. Hayes, A. M. Kitchen, B. H. Cochran, Proc. Natl. Acad. Sci. U.S.A. 84, 1272 To define the cell type(s) from which the daf-2 insulinlike signaling pathway functions to control C. elegans life-span, metabolism, and development, we restored daf-2 pathway function to restricted cell types by using distinct promoters to express daf-2 or age-1 cDNAs in either neurons, intestine, or muscle cells of a daf-2 or age-1 mutant (16 -22). Long life-span, metabolic changes, and dauer arrest were tested in these transgenic animals The long life-span of daf-2 and age-1 mutants was rescued by neuronal expression of daf-2 or age-1, respectively, with the panneuronal unc-14 promoter (16, 24). Neuronally restricted age-1 expression fully restored wild-type adult life-span to an age-1(mg44) null mutan
