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Personne :
Guillemette, Chantal

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Guillemette

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Chantal

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Université Laval. Faculté de pharmacie

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ncf13674031

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Voici les éléments 1 - 4 sur 4
  • PublicationAccès libre
    Immunohistochemical expression of conjugating UGT1A-derived splice proteins in normal and tumoral drug-metabolising tissues in humans
    (Wiley, 2010-10-29) Bellemare, Judith.; Pelletier, Georges; Popa, Ion; Têtu, Bernard; Harvey, Mario.; Guillemette, Chantal; Rouleau, Mélanie
    Glucuronidation by UDP-glucuronyltransferase (UGT) enzymes is the prevailing conjugative pathway for the metabolism of both xenobiotics and endogenous compounds. Alterations in this pathway, such as those generated by common genetic polymorphisms, have been shown to significantly impact on the health of individuals, influencing cancer susceptibility, responsiveness to drugs and drug-induced toxicity. Alternative usage of terminal exons leads to UGT1A-derived splice variants, namely the classical and enzymatically active isoforms 1 (i1) and the novel enzymatically inactive isoforms 2 (i2). In vitro functional data from heterologous expression and RNA interference experiments indicate that these i2 isoforms act as negative modulators of glucuronidation, likely by forming inactive complexes with active isoform 1. We used specific antibodies against either active i1 or inactive i2 proteins to examine their distribution in major drug-metabolizing tissues. Data revealed that UGT1A_i1 and inactive UGT1A_i2 are co-produced in the same tissue structures, including liver, kidney, stomach, intestine and colon. Examination of the cellular distribution and semi-quantitative level of expression of UGT1As revealed heterogeneous expression of i1 and i2 proteins, with increased expression of i2 in liver tumours and decreased levels of i1 and i2 in colon cancer specimens, compared to normal tissues. These differences in expression may be relevant to human colon and liver cancer tumorigenesis. Our data clearly demonstrate the similar immunolocalization of active and inactive UGT1A isoforms in most UGT1A-expressing cell types of major tissues involved in drug metabolism. These expression patterns are consistent with a dominant-negative function for the i2 encoded by the UGT1A gene.
  • PublicationAccès libre
    Unravelling the transcriptomic landscape of the major phase II UDP-glucuronosyltransferase drug metabolizing pathway using targeted RNA sequencing
    (Nature, 2015-04-14) Lévesque, Éric; Margaillan, Guillaume; Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Villeneuve, Lyne
    A comprehensive view of the human UDP-glucuronosyltransferase (UGT) transcriptome is a prerequisite to the establishment of an individual's UGT metabolic glucuronidation signature. Here, we uncover the transcriptome landscape of the 10 human UGT gene loci in normal and tumoral metabolic tissues by targeted RNA next-generation sequencing. Alignment on the human hg19 reference genome identifies 234 novel exon-exon junctions. We recover all previously known UGT1 and UGT2 enzyme-coding transcripts and identify over 130 structurally and functionally diverse novel UGT variants. We further expose a revised genomic structure of UGT loci and provide a comprehensive repertoire of transcripts for each UGT gene. Data also uncover a remodelling of the UGT transcriptome occurring in a tissue- and tumor-specific manner. The complex alternative splicing program regulating UGT expression and protein functions is likely critical in determining detoxification capacity of an organ and stress-related responses, with significant impact on drug responses and diseases.
  • PublicationAccès libre
    Pharmacogenomics of human uridine diphospho-glucuronosyltransferases (UGTs) and clinical implications
    (Wiley, 2014-06-12) Lévesque, Éric; Rouleau, Michèle; Guillemette, Chantal
    Glucuronidation, mediated by UDP-glucuronosyltransferase enzymes (UGTs), is a major phase II biotransformation pathway and, complementary to phase I metabolism and membrane transport, one of the most important cellular defense mechanism responsible for the inactivation of therapeutic drugs, other xenobiotics and numerous endogenous molecules. Individual variability in UGT enzymatic pathways is significant and may have profound pharmacological and toxicological implications. Several genetic and genomic processes are underlying this variability and are discussed in the context of drug metabolism and diseases such as cancer.
  • PublicationAccès libre
    Quantitative profiling of the UGT transcriptome in human drug metabolizing tissues
    (Nature Publishing Group., 2017-04-25) Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Guauque-Olarte, Sandra; Villeneuve, Lyne
    Alternative splicing as a mean to control gene expression and diversify function is suspected to considerably influence drug response and clearance. We report the quantitative expression profiles of the human UGT genes including alternatively spliced variants not previously annotated established by deep RNA-sequencing in tissues of pharmacological importance. We reveal a comprehensive quantification of the alternative UGT transcriptome that differ across tissues and among individuals. Alternative transcripts that comprise novel in-frame sequences associated or not with truncations of the 5′- and/or 3′- termini, significantly contribute to the total expression levels of each UGT1 and UGT2 gene averaging 21% in normal tissues, with expression of UGT2 variants surpassing those of UGT1. Quantitative data expose preferential tissue expression patterns and remodeling in favor of alternative variants upon tumorigenesis. These complex alternative splicing programs have the strong potential to contribute to interindividual variability in drug metabolism in addition to diversify the UGT proteome.