Over-expression of the p53B isoform, but not p53A, induces apoptosis in endocycling cells.

<p>(A) Left panel shows a map of the four predicted RNA transcripts for the <i>Drosophila</i> p53 gene based on cDNA and RNA-seq data annotated in Flybase. Exons are boxes, with predicted ORFs in orange, and 5′ or 3′ UTRs in gray. The right panel shows predicted protein isoform structures and sizes, with transactivation (TA) and DNA binding domains indicated by red and black boxes respectively. The protein domain predictions are adapted from Khoury and Bourdon (2010), which was based on protein alignment and needed further experimental confirmation <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004581#pgen.1004581-Khoury1" target="_blank">[99]</a>. (B–I) Activated Caspase-3 labeling in 3^rd instar larval wing discs (B–E) or salivary glands (F–I) after over-expression of <i>UAS:6XMyc:p53A</i> (C,G) or <i>UAS:6XMyc:p53B</i> (E,I) six hours after a 30 min heat pulse of <i>hsp70:GAL4</i> or no heat shock controls (B, D, F, H). Scale bars are 100 microns. (J) Quantification of the fluorescence intensity of Caspase-3 (C3) staining in the larval wing discs. Error bars represent S.E.M. for n = 4. ** p≤0.01, **** p≤0.0001. (K) Anti-Myc Western blot for Myc:p53 protein from adult wild type (WT) and different <i>UAS:p53</i> P element (P) or PhiC31 (PhiC) transgenic lines six hours after a 30 min heat pulse of <i>hsp70:GAL4</i> (HS), or no heat shock (No HS). Anti-alpha tubulin was used as a loading control.