Figure 3.—

Analysis of Su(z)2 alleles. (A) Structure of the wild-type Su(z)2 locus and insertions and deletions associated with Su(z)2 mutations. Psc (not shown) is located to the left. Exons 1–6 are shown as numbered rectangles. The RF is in red, and the HTH is in blue (exon 4–5 junction). Noncoding sequence is in gray. The TATA notation shown upstream of exon 1 is the putative TATA box identified 8 bp upstream of the Su(z)2^1.b7 breakpoint. R, EcoRI; N, NotI. (B) Frameshift, nonsense, and missense mutations associated with Su(z)2 mutations. Nonsense mutations are shown above the protein and are divided into two classes: those associated with a frameshift followed by a stop codon (FS*, top) and those associated with only a stop codon (*, bottom). Missense mutations are shown below the protein. The RF is shown in an exploded view, with bases that are altered by Su(z)2 mutations shown in black. Zn⁺⁺-coordinating residues are indicated. Su(z)2¹ (green), Su(z)2^4-34 (orange), Su(z)2^h29 (purple), and Su(z)2^s95 (blue) are complex and have been color coded to highlight the multiple mutations that they contain. Su(z)2¹ contains an L120F missense mutation and a K284* nonsense mutation. Both Su(z)2^4-31 and Su(z)2^4-34 contain an 8-bp deletion in exon 5 (not shown) that generates a three-amino-acid frameshift ending in a K238* nonsense codon (B). Su(z)2^4-34 differs from Su(z)2^4-31 in that it also contains an insertion (A) that has been localized to a 1.6-kb ClaI/BamHI fragment in the distal half of intron 1. Su(z)2^h29 contains a G-to-A transition that disrupts a 5′ acceptor site for exon 4 (A) and is predicted to result in a frameshift ending in a T186* nonsense codon (B). Su(z)2^s95 contains a roo or roo-like (A) and a Q370* nonsense codon (B). *, Su(z)2^1.b7, a derivative of Su(z)2¹, carries a deletion (A), a 4-bp insertion (TTCT, not shown) at the site of the deletion, and the K284* nonsense codon that is also present in Su(z)2¹ (B). We have not determined whether Su(z)2^1.b7 also contains the L120F missense mutation that is found in Su(z)2¹. Both A and B are drawn to scale.