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Poster Full Abstracts - Physiology and Aging
Poster board number is above title. The first author is the presenter
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Dose dependent stress response to high levels of Sir2 over-expression in flies.
Rachel E Whitaker, Shakeela Faulkner, Reika Miyokawa, Lucas Burhenn,
Will Donovan, Stephen Helfand. Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI.
It has been reported that a 10-25 fold increase in expression of dSir2 leads to cell lethality
1
. Based upon these studies it was concluded that dSir2 is highly
lethal to cells and the previous beneficial effects of increased dSir2 expression were due to the simultaneous expression of the neighboring DNAJ-H gene in
the particular overexpression system used
2
. We examined several new UAS-dSir2 transgenic lines with dSir2 expression of up to 360 fold over normal
without developmental lethality. Despite these transgenes being in locations distant from the DNAJ-H gene, we found DNAJ-H was up-regulated as much as
5-fold when dSir2 was expressed at very high levels, but not when only moderately over-expressed. Heat shock proteins Hsp27 and Hsp70 levels were found
to increase in the same pattern as DNAJ-H. This suggests that the DNAJ-H up-regulation noted by Griswold et al
1
is not related to its genetic location near
dSir2, but rather is a stress response to very high levels of dSir2. Recalculation of the levels of dSir2 in the “lethal” line from Griswold et al
1
using a gene-
switch inducible system which preserves the cells in which dSir2 is being expressed showed extraordinarily high levels of dSir2, at least double our highest
expressing line. Additionally, utilizing the gene switch system to express the “lethal” dSir2 transgenic lines at “lower” levels we found this line also up-
regulated both DNAJ-H and heat shock proteins, demonstrating that very high levels of dSir2 lead to the induction of stress responses. Our studies show that
it is unlikely that dSir2 normally plays a role in regulating cell death directly in over-expression studies. Instead, extremely high levels of dSir2 over-
expression are likely causing lethality due to protein stress pathways. 1. Griswold et al PNAS 2008 Jun 24;105(25):8673-8 2. Rogina et al PNAS 2004 Nov
9;101(45):15998-6003.