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1.  Characterization of a dominant-active STAT that promotes tumorigenesis in Drosophila 
Developmental biology  2010;344(2):621-636.
Little is known about the molecular mechanisms by which STAT proteins promote tumorigenesis. Drosophila is an ideal system for investigating this issue, as there is a single STAT (Stat92E), and its hyperactivation causes overgrowths resembling human tumors. Here we report the first identification of a dominant-active Stat92E protein, Stat92EΔNΔC, which lacks both N- and C-termini. Mis-expression of Stat92EΔNΔC in vivo causes melanotic tumors, while in vitro it transactivates a Stat92E-luciferase reporter in the absence of stimulation. These gain-of-function phenotypes require phosphorylation of Y711 and dimer formation with full-length Stat92E. Furthermore, a single point mutation, an R442P substitution in the DNA-binding domain, abolishes Stat92E function. Recombinant Stat92ER442P translocates to the nucleus following activation but fails to function in all assays tested. Interestingly, R442 is conserved in most STATs in higher organisms, suggesting conservation of function. Modeling of Stat92E indicates that R442 may contact the minor groove of DNA via invariant TC bases in the consensus binding element bound by all STAT proteins. We conclude that the N- and C- termini function unexpectedly in negatively regulating Stat92E activity, possibly by decreasing dimer dephosphorylation or increasing stability of DNA interaction, and that Stat92ER442 has a nuclear function by altering dimer:DNA binding.
PMCID: PMC2914209  PMID: 20501334
STAT; JAK; Unpaired; Drosophila; constitutively active; in vitro reporter; in vivo reporter; structure function; signal transduction
2.  A case study of the reproducibility of transcriptional reporter cell-based RNAi screens in Drosophila 
Genome Biology  2007;8(9):R203.
A second generation dsRNA library was used to re-assess factors that influence the outcome of transcriptional reporter-based whole-genome RNAi screens for the Wnt/Wingless (wg) and Hedgehog (hh)-signaling pathways.
Off-target effects have been demonstrated to be a major source of false-positives in RNA interference (RNAi) high-throughput screens. In this study, we re-assess the previously published transcriptional reporter-based whole-genome RNAi screens for the Wingless and Hedgehog signaling pathways using second generation double-stranded RNA libraries. Furthermore, we investigate other factors that may influence the outcome of such screens, including cell-type specificity, robustness of reporters, and assay normalization, which determine the efficacy of RNAi-knockdown of target genes.
PMCID: PMC2375041  PMID: 17903264

Results 1-2 (2)