Cytochrome c transcriptional activation and mRNA stability during contractile activity in skeletal muscle.
We evaluated contractile activity-induced alterations in cytochrome c transcriptional activation and mRNA stability with unilateral chronic stimulation (10 Hz, 3 h/day) of the rat tibialis anterior (TA) muscle for 1, 2, 3, 4, 5, and 7 days (n = 3-11/group). Transcriptional activation was assessed by direct plasmid DNA injection into the TA with a chloramphenicol acetyltransferase (CAT) reporter gene linked to 326 bp of the cytochrome c promoter. Cytochrome c mRNA in stimulated muscles increased by 1.3- to 1. 7-fold above control between 1 and 7 days. Cytochrome c protein was increased after 5 days of stimulation to reach levels that were 1. 9-fold higher than control by 7 days. Cytochrome c mRNA stability, determined with an in vitro decay assay, was greater in stimulated TA than in control between 2 and 4 days, likely mediated by the induction of a cytosolic factor. In contrast, cytochrome c transcriptional activation was elevated only after 5 days of stimulation when mRNA stability had returned to control levels. Thus the contractile activity-induced increase in cytochrome c mRNA was due to an early increase in mRNA stability, followed by an elevation in transcriptional activation, leading to an eventual increase in cytochrome c protein levels.
Freyssenet
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Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3.
Connor
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Takahashi
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Hood
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D000818:Animals; D003574:Cytochrome c Group / Q000235:genetics* / Q000378:metabolism; D004355:Drug Stability; D004558:Electric Stimulation; D006614:Hindlimb; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection; D001616:beta-Galactosidase / Q000378:metabolism
D003574:Cytochrome c Group; D012333:RNA, Messenger; D001616:beta-Galactosidase