Fig. 2. Recognition by Rump correlates with nos RNA localization signal function. (A) UV-crosslinking of MBP-Rump to radiolabeled nos +1 and +2' element RNA probes. (B) UV-crosslinking of MBP-Rump to radiolabeled +2' element RNA in the absence (0) or presence of 200-, 400- and 600-fold molar excess of unlabeled +2' or +1 element RNA. (C) Above is a diagram of the +2' element with the two CGUU motifs (A and D) indicated. The lightly shaded region is highly conserved between D. melanogaster and D. virilis (Bergsten et al., 2001). The portions of the +2' element retained in the deletion mutants (1-5) are indicated by solid bars. C-to-G point mutations in the CGUU motifs were introduced individually (A or D) or in combination (AD) into the full-length +2' element. Beneath is shown UV-crosslinking of MBP-Rump to the indicated radiolabeled RNA probes. (D) Diagram of the nos-tub:nos+2 transgene, which contains only the nos +1 and +2' localization elements. (E,F) In situ hybridization to nos in preblastoderm nos^BN embryos carrying (E) the nos-tub:nos+2 and (F) the nos-tub:nos+2(D)G:C transgenes. Because nos^BN embryos lack endogenous nos mRNA (Wang et al., 1994), only the transgenic mRNA is detected.