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dc.contributor.authorOsna, N.-
dc.contributor.authorWhite, R.-
dc.contributor.authorDonohue, T.-
dc.contributor.authorBeard, M.-
dc.contributor.authorTuma, D.-
dc.contributor.authorKharbanda, K.-
dc.identifier.citationBiochemical and Biophysical Research Communications, 2010; 391(2):1291-1296-
dc.description.abstractThe proteasome is a multi-catalytic protein degradation enzyme that is regulated by ethanol-induced oxidative stress; such suppression is attributed to CYP2E1-generated metabolites. However, under certain conditions, it appears that in addition to oxidative stress, other mechanisms are also involved in proteasome regulation. This study investigated whether impaired protein methylation that occurs during exposure of liver cells to ethanol, may contribute to suppression of proteasome activity. We measured the chymotrypsin-like proteasome activity in Huh7CYP cells, hepatocytes, liver cytosols and nuclear extracts or purified 20S proteasome under conditions that maintain or prevent protein methylation. Reduction of proteasome activity of hepatoma cell and hepatocytes by ethanol or tubercidin was prevented by simultaneous treatment with S-adenosylmethionine (SAM). Moreover, the tubercidin-induced decline in proteasome activity occurred in both nuclear and cytosolic fractions. In vitro exposure of cell cytosolic fractions or highly purified 20S proteasome to low SAM:S-adenosylhomocysteine (SAH) ratios in the buffer also suppressed proteasome function, indicating that one or more methyltransferase(s) may be associated with proteasomal subunits. Immunoblotting a purified 20S rabbit red cell proteasome preparation using methyl lysine-specific antibodies revealed a 25kDa proteasome subunit that showed positive reactivity with anti-methyl lysine. This reactivity was modified when 20S proteasome was exposed to differential SAM:SAH ratios. We conclude that impaired methylation of proteasome subunits suppressed proteasome activity in liver cells indicating an additional, yet novel mechanism of proteasome activity regulation by ethanol.-
dc.description.statementofresponsibilityNatalia A. Osna, Ronda L. White, Terrence M. Donohue Jr., Michael R. Beard, Dean J. Tuma and Kusum K. Kharbanda-
dc.publisherAcademic Press Inc-
dc.rightsCopyright © 2010 Published by Elsevier Inc.-
dc.subject20S proteasome-
dc.subjectHepatoma cells-
dc.subjectMethyl lysine-
dc.titleImpaired methylation as a novel mechanism for proteasome suppression in liver cells-
dc.typeJournal article-
dc.identifier.orcidBeard, M. [0000-0002-4106-1016]-
Appears in Collections:Aurora harvest
Molecular and Biomedical Science publications

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