Figure 4.

 Inversion of the 3′ half of the p50/p68-binding RNA fragment prevents posterior derepression in vivo. The orientation of the 3′ half of the fragment is indicated by an arrow. (A) m1m2lacwt, wild-type m1–m2 region, fused 3 nucleotides downstream of m2 to the lacZ reporter, under the regulatory control of wild-type osk 3′ UTR. Reporter RNA and protein distributions, as detected in situ by RNA hybridization and β-galactosidase activity, are virtually indistinguishable from those of endogenous osk. (B) m1INVm2lacwt, the p50/p68-binding fragment in the m1–m2 region of the reporter transgene was mutated by inversion of the 3′ half (see probe c). As in the wild-type construct, the RNA is efficiently localized; however, translation is not derepressed.