Fig. 1. Tagged nos and nos-tub3'UTR transgenes. (A) The gfp-nos and gfp-nos-tub3'UTR transgenes contain GFP sequences (dark shading) inserted at the N terminus of the genomic nos coding region (light shading). Both transgenes include the nos promoter and 5' regulatory sequences (Pnos), 5'UTR (left black bar) and polyadenylation signal. Gfp-nos (top) bears the intact nos 3'UTR (right black bar), whereas these sequences have been replaced by -tubulin 3'UTR sequences (tub) in gfp-nos-tub3'UTR (bottom). (B) The hemagglutinin (HA) epitope tagged nos-tub3'UTR transgene is identical to gfp-nos-tub3'UTR, except that an N-terminal HA tag replaces GFP. The nos-tub:TCE and TCE mutant transgenes carry insertions of wild-type and mutant TCE sequences (shown in C), respectively (hatched box). Transgenes in A and B are drawn to scale, except for introns. (C) Nucleotide changes associated with the SRE^– (circles), TCEIIA (squares) and TCEIIIA (hexagons) mutations are indicated on the TCE secondary structure. The following mutations are not shown: TCEIIIA/U^C72, a compensatory mutation to TCEIIIA that restores base pairing with three A to U substitutions; and TCEIIIGC/GC, which changes the alternating U-A and A-U base pairs in the distal region of stem-loop III to alternating G-C and G-C base pairs (Crucs et al., 2000).