Structure and expression of the Drosophila
Parp locus. (A) Deduced genomic structure of the
300-kb Parp region; open boxes are sequenced. The arrangement
of the exons encoding Parp-I is shown at top (Uchida et al.
1993; Hanai et al. 1998). (Bottom) The positions of three
unlinked Drosophila genomic contigs (thin black lines:
AE002935, AE002666, and AE002892) homologous to Parp-I exons are shown
at right (Adams et al. 2000). Pm1 indicates the Parp-I
promoter deduced from 5′ cDNA sequences (Hanai et al. 1998). A single
cDNA isolated from early ovarian stages, GM10715, defines the
alternatively spliced Parp-e transcript. The 5′-most 273 bp of GM10715
matches the genomic sequence flanking a P element insertion,
CH(3)1 (Zhang and Spradling 1994). A map of this region
(left portion of figure) was constructed by chromosome walking
using a P1 genomic library (Kimmerly et al. 1996) (bottom,
thick black lines). The two resulting scaffolds were sequenced and
found to span four small preexisting genomic sequence contigs (thin
black lines) and to link to a fifth (AE003403). The color code
indicates which portion of PARP is encoded: DNA binding (red),
automodification (purple), catalytic (blue), noncoding (green and
yellow). (B) Multiple Parp transcripts. A Northern
blot of poly(A)-containing RNA from the indicated developmental stages
reveals both a 3.2-kb RNA, the size predicted for Parp-I, and a 2.6-kb
RNA, the approximate size expected for Parp-II and Parp-e.
Parp-homologous RNAs are abundant in both ovaries and embryos,
and are reduced but still detectable in second instar larvae and
adults. (C) Whole mount in situ hybridization using a 1.4-kb
cDNA probe from the DNA-binding domain common to all isoforms labels
Parp RNA in nurse cells and in oocytes from stage 9–14
follicles. (D) RT-PCR using isoform-specific primers (see
diagrams) that distinguish between Parp-I (or Parp-II) and Parp-e
demonstrate that Parp-e is produced in ovaries and embryos, but not at
detectable levels in second instar larvae, or in adults outside the
ovary. (E) Nuclei are shown from brains of third instar larvae
expressing a Parp-I-DsRed fusion gene (see Materials and Methods).
Protein is abundant in the chromocenter (C), the nucleolus (N), and at
sites within euchromatin. (F) Third instar larval brain nuclei
stained with anti-poly(ADP-ribose) antibody 10H show that
protein-associated ADP-ribose is found in the same regions as
PARP-DsRed.