Fig. 4. Clustered LAG-1 binding sites are involved in the regulatory expression of lag-1 during AC/VU specification. The lag-1:: YFP expression patterns are summarized as a model. LAG-1/NICD transcriptional activator binds to the clustered 13 LAG-1 binding sites, to express lag-1 in the pre-AC/pre-VU and VU as well as their descendants. lag-1 expression disappears in the AC at mid L2, immediately after its fate becomes specified. When the LAG-1 binding sites are mutated, lag-1 expression in the AC is retained until L3 molt, suggesting the existence of a cryptic AC-specific enhancer in lag-1, which is suppressed by LAG-1 repressor in wild-type animals.