title: Cooperative regulation of the interferon regulatory factor-1 tumor suppressor protein by core components of the molecular chaperone machinery.
abstract: Our understanding of the post-translational processes involved in regulating the interferon regulatory factor-1 (IRF-1) tumor suppressor protein is limited. The introduction of mutations within the C-terminal Mf1 domain (amino acids 301-325) impacts on IRF-1-mediated gene repression and growth suppression as well as the rate of IRF-1 degradation. However, nothing is known about the proteins that interact with this region to modulate IRF-1 function. A biochemical screen for Mf1-interacting proteins has identified an LXXLL motif that is required for binding of Hsp70 family members and cooperation with Hsp90 to regulate IRF-1 turnover and activity. These conclusions are supported by the finding that Hsp90 inhibitors suppress IRF-1-dependent transcription shortly after treatment, although at later time points inhibition of Hsp90 leads to an Hsp70-dependent depletion of nuclear IRF-1. Conversely, the half-life of IRF-1 is increased by Hsp90 in an ATPase-dependent manner leading to the accumulation of nuclear but not cytoplasmic IRF-1. This study begins to elucidate the role of the Mf1 domain of IRF-1 in orchestrating the recruitment of regulatory factors that can impact on both its turnover and transcriptional activity.
authors.affiliation: Cancer Research UK Interferon and Cell Signalling Group, Cell Signalling Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, Scotland, United Kingdom.
authors.forename: Vikram
authors.initials: V
authors.lastname: Narayan
authors.forename: Mirjam
authors.initials: M
authors.lastname: Eckert
authors.forename: Alicja
authors.initials: A
authors.lastname: Zylicz
authors.forename: Maciej
authors.initials: M
authors.lastname: Zylicz
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Ball
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D002460:Cell Line; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D025521:Tumor Suppressor Proteins