title: The TRAF-interacting protein (TRAIP) is a novel E2F target with peak expression in mitosis.
abstract: The TRAF-interacting protein (TRAIP) is an E3 ubiquitin ligase required for cell proliferation. TRAIP mRNA is downregulated in human keratinocytes after inhibition of the PI3K/AKT/mTOR signaling. Since E2F transcription factors are downstream of PI3K/AKT/mTOR we investigated whether they regulate TRAIP expression. E2F1 expression significantly increased the TRAIP mRNA level in HeLa cells. Reporter assays with the 1400 bp 5'-upstream promoter in HeLa cells and human keratinocytes showed that E2F1-, E2F2- and E2F4-induced upregulation of TRAIP expression is mediated by 168 bp upstream of the translation start site. Mutating the E2F binding site within this fragment reduced the E2F1- and E2F2-dependent promoter activities and protein-DNA complex formation in gel shift assays. Abundance of TRAIP mRNA and protein was regulated by the cell cycle with a peak in G2/M. Expression of GFP and TRAIP-GFP demonstrated that TRAIP-GFP protein has a lower steady-state concentration than GFP despite similar mRNA levels. Cycloheximide inhibition experiments indicated that the TRAIP protein has a half-life of around four hours. Therefore, the combination of cell cycle-dependent transcription of the TRAIP gene by E2F and rapid protein degradation leads to cell cycle-dependent expression with a maximum in G2/M. These findings suggest that TRAIP has important functions in mitosis and tumorigenesis.
authors.affiliation: Service of Dermatology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Chapard
authors.affiliation: Service of Dermatology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hohl
authors.affiliation: Service of Dermatology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Marcel
authors.initials: M
authors.lastname: Huber
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D003513:Cycloheximide / Q000737:chemistry; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D050703:E2F2 Transcription Factor / Q000378:metabolism*; D050704:E2F4 Transcription Factor / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015603:Keratinocytes / Q000166:cytology; D051379:Mice; D008938:Mitosis; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050703:E2F2 Transcription Factor; C493761:E2F2 protein, human; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins; D003513:Cycloheximide; C000607340:TRAIP protein, human; D044767:Ubiquitin-Protein Ligases
keywords: E2F transcription factor; TRAF-Interacting protein; TRAIP; cell cycle; promoter regulation