Journal Article

Distinct 5′ UTRs regulate XIAP expression under normal growth conditions and during cellular stress

Alura Riley, Lindsay E. Jordan and Martin Holcik

in Nucleic Acids Research

Volume 38, issue 14, pages 4665-4674
Published in print August 2010 | ISSN: 0305-1048
Published online April 2010 | e-ISSN: 1362-4962 | DOI: http://dx.doi.org/10.1093/nar/gkq241

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X-chromosome linked inhibitor of apoptosis, XIAP, is cellular caspase inhibitor and a key regulator of apoptosis. We and others have previously shown that XIAP expression is regulated primarily at the level of protein synthesis; the 5′ untranslated region (UTR) of XIAP mRNA contains an Internal Ribosome Entry Site (IRES) that supports cap-independent expression of XIAP protein during conditions of pathophysiological stress, such as serum deprivation or gamma irradiation. Here, we show that XIAP is encoded by two distinct mRNAs that differ in their 5′ UTRs. We further show that the dominant, shorter, 5′ UTR promotes a basal level of XIAP expression under normal growth conditions. In contrast, the less abundant longer 5′ UTR contains an IRES and supports cap-independent translation during stress. Our data suggest that the combination of alternate regulatory regions and distinct translational initiation modes is critical in maintaining XIAP levels in response to cellular stress and may represent a general mechanism of cellular adaptation.

Journal Article.  5684 words.  Illustrated.

Subjects: Chemistry ; Biochemistry ; Bioinformatics and Computational Biology ; Genetics and Genomics ; Molecular and Cell Biology

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