Figure 1.—

The dec-1 gene, proteins, and mutant transgene constructs. (A) The dec-1 gene. Open reading frames (ORFs) are denoted by rectangles. Sans the six C-terminal amino acids, the entire fc106 ORF (open rectangles, 950 amino acids) is present in the minor DEC-1 proproteins, fc125 and fc177. The solid rectangle represents a small ORF shared by fc125 and fc177; the fc177-specific ORF is shaded; the patterned rectangle denotes the fc125-specific ORF. The third intron contains two alternative 3′ splice acceptor sites. The (b1) pathway is used for fc106 mRNA; pathway (a1) is used for fc125 and fc177 mRNAs. The fc106- specific ORF is terminated in exon 4 after 18 bases. The fc177-specific ORF is removed from the fc106 and fc125 mRNAs via the (a2) splicing pathway. The large downward arrow shows the location of the dec1^ct4b1 breakpoint within the dec-1 gene. The small downward arrow represents the AG → TG dinucleotide change at the fc106-specific splice acceptor site in the dec-1⁴ allele. Key restriction sites used in constructing the fc106 cDNA transgene and its mutated derivatives included X (XhoI), A (ApaI), Hc (HincII), and Z (XbaI). (B) DEC-1 proproteins and processing of fc106. The three DEC-1 proproteins fc177, fc125, and fc106 with ORF designations as in A are shown. The timing and regions of fc106 that are separated by cleavage (s25, s80, s20, and s60) are indicated. The open reading frames used to produce the DEC-1 antisera used in this study (Nfc106, Ns80, and Cfc106) are indicated below the cleaved derivatives. (C) Construction of the dec-1 fc106 cDNA transgene and its mutant derivatives. The dec-1 gene is shown at the top; the line below the ApaI–HincII region indicates sequences that were derived from an fc106 cDNA (Hawley and Waring 1988). The coding region (rectangles) and 3′-UTR (line) of the fc106 cDNA transgene are shown below the dec-1 gene. Coding regions that were deleted (spaces) in the mutant fc106 cDNA transgenes and the positions of the primer pairs used in their construction are indicated (the forward vector primer used for the 5′-PCR fragment of the Q²⁰–E⁴⁷³ construct is not shown). All of the transgenes contained ∼2 kb of 5′-flanking and 1 kb of 3′-flanking dec-1 DNA in addition to the regions shown.