title: 4-Phenylbutyrate stimulates Hsp70 expression through the Elp2 component of elongator and STAT-3 in cystic fibrosis epithelial cells.
abstract: Sodium 4-phenylbutyrate (4PBA) corrects trafficking of ΔF508-CFTR in Cystic Fibrosis (CF) epithelia, which is hypothesized to, at least in part, result from increased expression of Hsp70 (stress-induced 70 kDa heat shock protein). To identify other 4PBA-regulated proteins that may promote correction of ΔF508 trafficking, we performed differential display RT-PCR on mRNA from IB3-1 CF bronchiolar epithelial cells treated for 0-24 h with 1 mM 4PBA. In this screen, a STAT-3 (signal transducer and activator of transcription-3)-interacting protein, StIP-1 that regulates STAT-3 activation had transiently increased expression. StIP-1 is identical to Elongator protein 2 (Elp2), a component of the Elongator complex that regulates RNA polymerase II. Previous studies have suggested that Elongator regulates Hsp70 mRNA transcription, and that the Hsp70 promoter contains functional STAT-3-binding sites. We therefore tested the hypothesis that 4PBA increases Hsp70 expression by an Elongator- and STAT-3-dependent mechanism. 4PBA treatment of IB3-1 CF bronchiolar epithelial cells caused transiently increased expression of Hsp70 protein, as well as Elp2 protein and mRNA. Elp2 depletion by transfection of small interfering RNAs, reduced both Elp2 and Hsp70 protein expression. 4PBA also caused transient activation of STAT-3, and increased abundance of nuclear proteins that bind to the STAT-3-responsive element of the Hsp70 promoter. Luciferase reporter assays demonstrated that both Elp2 overexpression and 4PBA increase Hsp70 promoter activity, while Elp2 depletion blocked the ability of 4PBA to stimulate Hsp70 promoter activity. Together, these data suggest that Elp2 and STAT-3 mediate, at least in part, the stimulation of Hsp70 expression by 4PBA.
authors: Division of Pulmonary Medicine and Cystic Fibrosis Center, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
authors: Laurence
authors: L
authors: Suaud
authors: Katelyn
authors: K
authors: Miller
authors: Ashley E
authors: AE
authors: Panichelli
authors: Rachel L
authors: RL
authors: Randell
authors: Catherine M
authors: CM
authors: Marando
authors: Ronald C
authors: RC
authors: Rubenstein
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D010654:Phenylbutyrates / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020545:Respiratory Mucosa / Q000378:metabolism* / Q000473:pathology; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C413649:ELP2 protein, human; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010654:Phenylbutyrates; D012333:RNA, Messenger; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C079373:STIP1 protein, human; C075773:4-phenylbutyric acid; D012319:RNA Polymerase II