Regulatory features of transcription in isolated mitochondria from
artemia franciscana embryos.
Eads, Brian D., and Steven C. Hand.
Department of EPO Biology, University of Colorado, Boulder, CO
80309-0334 USA
APStracts 6:0318R, 1999.
Optimal conditions were developed for an in organello transcriptional
run-on assay using mitochondria isolated from Artemia franciscana
embryos to investigate potential regulatory features of RNA synthesis
under conditions of anoxia-induced quiescence. Transcription is not
dependent upon oxidative phosphorylation for maximal activity when
exogenous ATP is available. Bonafide transcription products, as
assessed by hybridization with specific mitochondrial cDNAs from A.
franciscana, are produced in an inhibitor-sensitive manner.
Transcription rate measured at pH 7.9 is reduced 80% when pH is
lowered to 6.3, a pH range that mimics the in vivo change seen upon
exposure of embryos to anoxia. The proton sensitivity of
mitochondrial RNA synthesis may provide a mechanism to depress this
significant energy expenditure during quiescence. The influence of
nucleotide concentration on kinetics is complicated by an
interdependence among nucleotide species. ATP inhibition observed at
subsaturating UTP concentrations is relieved when UTP is at
saturating, physiologically relevant levels. Taken together, these
data suggest that local (versus nuclear mediated) control is
important in dictating mitochondrial transcription during rapid
modulations in gene expresssion, like those observed under anoxia
-induced quiescence.
Received 2 April 1999; accepted in final form 27 July 1999.
APS Manuscript Number R207-9.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 9 August 1999