Inactivation of IkappaB contributes to transcriptional activation of spermidine/spermine N(1)-acetyltransferase

Molecular Carcinogenesis
Woonyoung ChoiWei Zhang

Abstract

Spermidine/spermine N(1)-acetyltransferase (SSAT) is a key enzyme in polyamine catabolism. We recently reported that the combination of N(1), N(11)-diethylnorspermine (DENSPM) and 5-fluorouracil (5-FU) synergistically induces SSAT expression, depletes polyamine levels and causes apoptosis in colon cancer cells. To determine whether new RNA and protein synthesis is required for SSAT induction, we examined the effect of actinomycin D (ActD) and cycloheximide (CHX). ActD alone blocked the induction of SSAT expression; however, the combination of CHX and DENSPM markedly induced SSAT expression and caused mitochondrial damage, suggesting that an inhibitory labile protein is involved in SSAT transactivation. SSAT promoter analysis identified two putative Rel/Nuclear Factor kappaB (NFkappaB) binding sites. Thus, we hypothesized that IkappaB is the labile inhibitory protein and that its removal contributes to the activation of NFkappaB. CHX quickly eliminated the IkappaB protein in the cells and increased the levels of the two subunits of NFkappaB, p65 and p50, in the nucleus. Luciferase reporter gene assay showed that SSAT promoter constructs containing the two putative NFkappaB binding elements responded to CHX as well as TNFalpha, w...Continue Reading

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Citations

Apr 20, 2011·Journal of Psychiatric Research·Laura M Fiori, Gustavo Turecki
Jul 11, 2009·The Biochemical Journal·Robert A Casero, Anthony E Pegg
Mar 20, 2008·American Journal of Physiology. Endocrinology and Metabolism·Anthony E Pegg

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