Figure 1

echinus gene structure, mutants and surrounding genomic region. Echinus (CG2904) exons are indicated by shaded boxes. Exons are numbered sequentially with respect to the 5' end of the gene. The shaded boxes with diagonal lines represent the conserved USP domain. Three different splice versions identified through cDNA sequencing are illustrated in panels A-C. Exons common to all three splice versions are noted with lines above numbered exons 7,8, and 9. Nearby genes are indicated (open arrows), as are Flybase annotated P element insertions, and ec^PlacZ. Open triangles indicate P element insertions that are wildtype with respect to echinus, while filled triangles indicate P element insertion lines with rough eyes that fail to complement echinus. The location of EMS-induced point mutations in echinus, ec⁵⁶ and ec^3c3, and mutations identified in ec¹ (a point mutation and a Copia insertion) are indicated by asterisks. The locations of the breakpoints for the echinus deletion alleles ec^EPΔ4 and ec^Δ9 are indicated by dotted lines at the top. (A) ec-SF1 encodes a version of echinus that contains Cys and His box residues important for USP catalysis, as noted by the highlighted residues. These and surrounding sequences are highly conserved in predicted echinus homologs in other insect species. Highly related sequences are also found in a number of other species. (B) The ec-SF2 transcript initiates at a downstream exon, which contains an initial methionine and coding sequences that lack a Cys box. The 3' exon containing His box sequences (exon 9) is still present. (C) The ec-SF3 transcript initiates at a distinct position further 3', and also contains His box sequences, but lacks Cys box sequences. Sequences highly related to this alternative N-terminus are also found in a number of other species.