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Fig. 5. Genetic and molecular models for LIN-46 activity in developmental timing.
(A) Genetic models for the heterochronic pathway governing fate choices at two
stages. (Left) Interactions governing the L2/L3 fate choice. The circled
regulators x and y have not been identified and may in fact
represent multiple factors. lin-14 is depicted in its role in the
L2/L3 fate decision only (lin-14B activity). The position of
daf-12 is based on previous studies
(Antebi et al., 1998;
Seggerson et al., 2002); its
role does not appear to be analogous to that of lin-46. (Right)
Interactions governing the L/A switch. The effect of lin-28 or
lin-46 on let-7 expression or activity has not been
determined, and may be indirect. The linear pathway from let-7 to
adult fates is based on previous studies
(Abrahante et al., 2003;
Lin et al., 2003). (B) A
molecular model for LIN-46 protein function. LIN-46 may scaffold a
multiprotein assembly constituting a developmental timing complex that
regulates the expression of downstream heterochronic genes and promotes L3-
and adult-specific cell fates. Broken arrow indicates that the effects of the
complex may be either positive or negative, and either direct or indirect.
LIN-28 may act as a negative regulator of one or more components of that
complex, probably at the level of gene expression.
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