title: Heat shock-independent induction of multidrug resistance by heat shock factor 1.
abstract: The screening of two different retroviral cDNA expression libraries to select genes that confer constitutive doxorubicin resistance has in both cases resulted in the isolation of the heat shock factor 1 (HSF1) transcription factor. We show that HSF1 induces a multidrug resistance phenotype that occurs in the absence of heat shock or cellular stress and is mediated at least in part through the constitutive activation of the multidrug resistance gene 1 (MDR-1). This drug resistance phenotype does not correlate with an increased expression of heat shock-responsive genes (heat shock protein genes, or HSPs). In addition, HSF1 mutants lacking HSP gene activation are also capable of conferring multidrug resistance, and only hypophosphorylated HSF1 complexes accumulate in transduced cells. Our results indicate that HSF1 can activate MDR-1 expression in a stress-independent manner that differs from the canonical heat shock-activated mechanism involved in HSP induction. We further provide evidence that the induction of MDR-1 expression occurs at a posttranscriptional level, revealing a novel undocumented role for hypophosphorylated HSF1 in posttranscriptional gene regulation.
authors.affiliation: Unité de Génétique Moléculaire et Intégrations des Fonctions Cellulaires, CNRS-UPR1983, 7 rue Guy Moquet, BP8, 94801 Villejuif Cedex, France. tchenio@infobiogen.fr
authors.forename: Thierry
authors.initials: T
authors.lastname: Tchénio
authors.forename: Marilyne
authors.initials: M
authors.lastname: Havard
authors.forename: Luis A
authors.initials: LA
authors.lastname: Martinez
authors.forename: François
authors.initials: F
authors.lastname: Dautry
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000502:physiology*; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D015723:Gene Library; D019450:Genes, MDR; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response / Q000502:physiology*; D006801:Humans; D009154:Mutation; D010766:Phosphorylation; D012323:RNA Processing, Post-Transcriptional; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D000076249:Heat Shock Transcription Factors; D014157:Transcription Factors; D004317:Doxorubicin