Figure 4.—
Fc106 accumulates and is processed in the absence of its evolutionarily conserved C terminus. (A) A schematic of fc106. The truncated line below the schematic indicates the region present in the fc106ΔG922–R949 transgene. The sequence shows the 50 C-terminal amino acids of fc106. Amino acids that are identical in the D. melanogaster and D. virilis fc106 proproteins are in boldface type; the amino acids deleted in fc106ΔG922–R949 are underlined. The Cfc106 antiserum (above the schematic) was used in B–E. (B) Western blot of SDS-soluble proteins from staged egg chambers isolated from homozygous DEC-1 null females (dec-129) in the absence (29) or presence of the fc106ΔG922–R949 transgene (29;*D). The positions of fc106-, s80-, and s60-like derivatives (fc106D, s80D, and s60D) are indicated; egg chamber stages are shown at the bottom of the lanes. (C–E) Western blots of SDS-soluble proteins from stage 10 (C) and 14 (D and E) egg chamber proteins resolved using a Mini-Protean electrophoresis cell system. In C the positions of the variant DEC-1 forms fc106V and s80V produced by homozygous white females (w) are shown (lane 1) along with fc125 and s95 produced by the dec-14 allele in heterozygous dec-14/dec-129 (4/29) females (lane 5). A wild-type fc106 cDNA transgene (*) or a mutant fc106ΔG922–R949 transgene (*D) was introduced into white (lanes 2 and 3) or dec-14/dec-129 females (lane 4) as indicated. The positions of the fc106ΔG922–R949 fc106-like and s80-like derivatives are indicated (..) in lane 4. (D) A Western blot showing DEC-1 proteins in stage 14 egg chambers. The genotypes of the females are as described in C. The positions of variant s60 (s60V) (lane 1), s60 from the fc106 cDNA transgene (.) (lane 2), and s60 produced from fc106ΔG922–R949 (s60D) (lanes 3 and 4) are indicated. In lane 4, s80 represents a C-terminal product produced by cleavage of s95 (see E, lane 6) and perhaps some s80-like derivative from fc106ΔG922–R949 that has yet to be cleaved. (E) Western blot of stage 14 egg chambers from Oregon R P2-strain females (S) showing the positions of the standard forms of the s80 and s60 DEC-1 proteins (lane 5) and from homozygous dec-14 females (4) showing the cleaved C-terminal derivative of s95 that migrates in the 80-kDa size range (lane 6).