Overexpressing USP Blocks the Synthesis of Glue Proteins.

<p>Protein extracts were prepared from salivary glands of seven different crosses at the wandering-L3 stage. Two SDS-PAGE gels were produced, one was fixed and stained (C) and the other was blotted. The blot was cut, and one section was incubated with the Tubulin loading control (A), while the other was incubated with an antibody against DsRED (B). The first three crosses serve as controls for protein levels in the parental stock (<i>w¹¹¹⁸</i>), the “responder only” cross (<i>w¹¹¹⁸ x USP+</i>), and the “tester only” cross (<i>w¹¹¹⁸ x sgGal4</i>; <i>glueRED</i>). The remaining 4 crosses were the tester stock (<i>sgGal4</i>; <i>glueRED</i>) crossed to <i>EcR-DN</i>, <i>EcRi</i>, <i>USPi</i>, and <i>USP+</i>. Note that all glue-protein bands from the stained gel are reduced by the <i>EcR-DN</i>, <i>EcRi</i>, and <i>USP+</i> reagents (but not <i>USPi</i>) as predicted by the model that glue-genes are induced by 20E through a receptor that requires EcR but not USP. The position of the major glue proteins (arrows) correspond to band sizes observed when secreted glue plugs were precipitated with ethanol and subjected to SDS/PAGE.