The Drosophila heterochromatic gene encoding poly(ADP-ribose) polymerase (PARP) is required to modulate chromatin structure during development.
Poly(ADP-ribose) polymerase (PARP) is a major NAD-dependent modifying enzyme that mediates important steps in DNA repair, transcription, and apoptosis, but its role during development is poorly understood. We found that a single Drosophila Parp gene spans more than 150 kb of transposon-rich centromeric heterochromatin and produces several differentially spliced transcripts, including a novel isoform, PARP-e, predicted to encode a protein lacking enzymatic activity. An insertion mutation near the upstream promoter for Parp-e disrupts all Parp expression. Heterochromatic but not euchromatic sequences become hypersensitive to micrococcal nuclease, nucleoli fail to form, and transcript levels of the copia retrotransposon are elevated more than 50-fold; the variegated expression of certain transgenes is dominantly enhanced. Larval lethality can be rescued and PARP activity restored by expressing a cDNA encoding PARP-e. We propose that PARP-e autoregulates Parp transcription by influencing the chromatin structure of its heterochromatic environment. Our results indicate that Parp plays a fundamental role organizing the structure of Drosophila chromatin.
Howard Hughes Medical Research Laboratories, Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland 21210, USA.
Alexei
A
Tulin
Dianne
D
Stewart
Allan C
AC
Spradling
D000818:Animals; D015152:Blotting, Northern; D002466:Cell Nucleolus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D002874:Chromosome Mapping; D002875:Chromosomes / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004251:DNA Transposable Elements; D018076:DNA, Complementary / Q000378:metabolism; D004330:Drosophila / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D005838:Genotype; D006570:Heterochromatin / Q000235:genetics* / Q000378:metabolism*; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008836:Micrococcal Nuclease / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D009154:Mutation; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D002843:Chromatin; D004251:DNA Transposable Elements; D018076:DNA, Complementary; D006570:Heterochromatin; D020033:Protein Isoforms; D012333:RNA, Messenger; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases; D008836:Micrococcal Nuclease