title: Protein kinase A binds and activates heat shock factor 1.
abstract: BACKGROUND
  Many inducible transcription factors are regulated through batteries of posttranslational modifications that couple their activity to inducing stimuli. We have studied such regulation of Heat Shock Factor 1 (HSF1), a key protein in control of the heat shock response, and a participant in carcinogenisis, neurological health and aging. As the mechanisms involved in the intracellular regulation of HSF1 in good health and its dysregulation in disease are still incomplete we are investigating the role of posttranslational modifications in such regulation.
  
  
  RESULTS
  In a proteomic study of HSF1 binding partners, we have discovered its association with the pleiotropic protein kinase A (PKA). HSF1 binds avidly to the catalytic subunit of PKA, (PKAcα) and becomes phosphorylated on a novel serine phosphorylation site within its central regulatory domain (serine 320 or S320), both in vitro and in vivo. Intracellular PKAcα levels and phosphorylation of HSF1 at S320 were both required for HSF1 to be localized to the nucleus, bind to response elements in the promoter of an HSF1 target gene (hsp70.1) and activate hsp70.1 after stress. Reduction in PKAcα levels by small hairpin RNA led to HSF1 exclusion from the nucleus, its exodus from the hsp70.1 promoter and decreased hsp70.1 transcription. Likewise, null mutation of HSF1 at S320 by alanine substitution for serine led to an HSF1 species excluded from the nucleus and deficient in hsp70.1 activation.
  
  
  CONCLUSIONS
  These findings of PKA regulation of HSF1 through S320 phosphorylation add to our knowledge of the signaling networks converging on this factor and may contribute to elucidating its complex roles in the stress response and understanding HSF1 dysregulation in disease.
authors.affiliation: Molecular and Cellular Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Ayesha
authors.initials: A
authors.lastname: Murshid
authors.forename: Shiuh-Dih
authors.initials: SD
authors.lastname: Chou
authors.forename: Thomas
authors.initials: T
authors.lastname: Prince
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ajit
authors.initials: A
authors.lastname: Bharti
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Calderwood
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites / Q000235:genetics; D020134:Catalytic Domain / Q000235:genetics; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006367:HeLa Cells; D000076249:Heat Shock Transcription Factors; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D034622:RNA Interference; D020218:Response Elements / Q000235:genetics; D012694:Serine / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D014157:Transcription Factors; C081884:heat-shock protein 70.1; D049452:Green Fluorescent Proteins; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases