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Molecular and Cellular Biology, May 2005, p. 4075-4091, Vol. 25, No. 10
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.10.4075-4091.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Molecular & Integrative Physiology,1 Department of Computer Science, University of Illinois, Urbana, Illinois2
Received 16 September 2004/ Returned for modification 19 October 2004/ Accepted 23 February 2005
In contrast to previous steady-state analyses of the O2-responsive transcriptome, here we examined the dynamics of the response to short-term anaerobiosis (2 generations) in both catabolite-repressed (glucose) and derepressed (galactose) cells, assessed the specific role that Msn2 and Msn4 play in mediating the response, and identified gene networks using a novel clustering approach. Upon shifting cells to anaerobic conditions in galactose medium, there was an acute (
10 min) yet transient (<45 min) induction of Msn2- and/or Msn4-regulated genes associated with the remodeling of reserve energy and catabolic pathways during the switch from mixed respiro-fermentative to strictly fermentative growth. Concomitantly, MCB- and SCB-regulated networks associated with the G1/S transition of the cell cycle were transiently down-regulated along with rRNA processing genes containing PAC and RRPE motifs. Remarkably, none of these gene networks were differentially expressed when cells were shifted in glucose, suggesting that a metabolically derived signal arising from the abrupt cessation of respiration, rather than O2 deprivation per se, elicits this "stress response." By
0.2 generation of anaerobiosis in both media, more chronic, heme-dependent effects were observed, including the down-regulation of Hap1-regulated networks, derepression of Rox1-regulated networks, and activation of Upc2-regulated ones. Changes in these networks result in the functional remodeling of the cell wall, sterol and sphingolipid metabolism, and dissimilatory pathways required for long-term anaerobiosis. Overall, this study reveals that the acute withdrawal of oxygen can invoke a metabolic state-dependent "stress response" but that acclimatization to oxygen deprivation is a relatively slow process involving complex changes primarily in heme-regulated gene networks.
Supplemental material for this article may be found at http://mcb.asm.org/.
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