Figure 3.

Base-pairing disruption of the U3 3′-hinge with ETS region E1. Intact endogenous U3 snoRNA was depleted by antisense oligonucleotide injection into oocyte nuclei. Subsequently, synthetic wild-type or mutated U3 was injected, and the restoration of 18S rRNA production was assayed by in vivo labeling with ³²P-UTP, gel electrophoresis and autoradiography. The amount of 18S rRNA produced was quantified (see Materials and Methods) to normalize for any loading differences between gel lanes. Left panel: increasing disruption of base pairing at the left side of the 3′H–E1 interaction; right panel: increasing disruption of base pairing at the right side of the 3′H–E1 interaction.