ABSTRACT
Apoptotic cell death is accompanied by degradation of chromosomal DNA. Here, we established in Drosophila a null mutation in the gene for inhibitor of caspase-activated DNase (ICAD) by P-element insertion. We also identified a loss-of-function mutant in Drosophila for DNase II-like acid DNase. The flies deficient in the ICAD gene did not express CAD, and did not undergo apoptotic DNA fragmentation during embryogenesis and oogenesis. In contrast, the deficiency of DNase II enhanced the apoptotic DNA fragmentation in the embryos and ovary, but paradoxically, the mutant flies accumulated a large amount of DNA, particularly in the ovary. This accumulation of DNA in the DNase II mutants caused the constitutive expression of the antibacterial genes for diptericin and attacin, which are usually activated during bacterial infection. The expression of these genes was further enhanced in flies lacking both dICAD and DNase II. These results indicated that CAD and DNase II work independently to degrade chromosomal DNA during apoptosis, and if the DNA is left undigested, it can activate the innate immunity in Drosophila.
Subject(s)
Apoptosis/physiology , Drosophila Proteins , Drosophila melanogaster/immunology , Endodeoxyribonucleases/genetics , Proteins/genetics , Amino Acid Sequence , Animals , Animals, Genetically Modified , Apoptosis Regulatory Proteins , Chromosomes/genetics , DNA Primers/chemistry , Drosophila melanogaster/genetics , Endodeoxyribonucleases/antagonists & inhibitors , Enzyme Activation , Female , Humans , Immunity, Innate/physiology , Insect Proteins/genetics , Insect Proteins/metabolism , Male , Molecular Sequence Data , Mutagenesis, Site-Directed , Ovary/cytology , Ovary/metabolism , Proteins/immunology , Rabbits , Recombinant Proteins/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Sequence Homology, Amino Acid , Shock, Septic/pathologyABSTRACT
We have cloned a novel Drosophila melanogaster homeobox (Hbox) containing gene, NK-7.1 (Dm.HboxNK-7.1), which is located at 88B3 on the chromosome map, and is 1.5 kb downstream of the spn-B gene. The newly identified gene is expressed at high levels in the embryo, is switched off during larval and pupal stages, and is expressed again in the adult. The Hbox is highly similar to NK-1/S59 (Drosophila) and NK-3/bap (Drosophila). The amino acid (aa) identity ratios (%) were 58 between NK-7.1 and NK-1/S59, and between NK-7.1 and NK-3/bap. The other characteristic structures are the presence of homopolymeric aa stretches consisting of Q, N, and E.
