The molecular genetics of the bithorax complex of Drosophila: characterization of the products of the Abdominal-B domain.
In Drosophila the Abdominal-B (Abd-B) domain of the bithorax complex specifies the identities of several posterior abdominal segments, comprises homeo-protein-coding regions and cis-regulatory regions, and extends from infra-abdominal-5 (iab-5) to iab-8, inclusive. Mutations that eliminate the Abd-B domain act as late embryonic lethals and result in transformations of posterior abdominal segments toward more anterior ones. The Abd-B domain gives rise to a minimum of five homeo-box-containing transcripts, 7.8, 4.7, 4.3, 3.7, and 3.3 kb in length. We examined the structure of the Abd-B domain by sequencing two Abd-B cDNA clones derived from the 4.3- and the 4.7-kb transcripts and the corresponding genomic DNA. The domain spans approximately 100 kb and contains at least eight exons. The 4.7- and 4.3-kb transcripts contain an open reading frame capable of encoding a 54-kD protein. A portion of the deduced protein-coding sequence common to all of the Abd-B transcripts was cloned into an expression vector. The resultant fusion protein then was used to derive a monoclonal antibody specific to Abd-B. By use of that antibody, we identified two embryonic Abd-B proteins, 54 and 36 kD and determined the sum of their segmental distribution by immunohistochemical analysis of whole-mounted embryos and immunofluorescent analysis of dissected embryonic nervous systems. The proteins are distributed in the fourth to the ninth abdominal segments [parasegments (PS) 10-15] inclusive. Embryos homozygous for Polycomb (Pc) show labeling over almost the entire embryo, whereas embryos deficient for the Abd-B domain show no detectable labeling.
Celniker
S E
SE
Division of Biology, California Institute of Technology, Pasadena 91125.
Keelan
D J
DJ
Lewis
E B
EB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000032:analysis; D005314:Embryonic and Fetal Development; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D018398:Homeodomain Proteins; D006801:Humans; D007301:Insect Hormones / Q000032:analysis / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012689:Sequence Homology, Nucleic Acid
C062393:Abd-B proteins, Drosophila; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D007301:Insect Hormones; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D004247:DNA