Functional interaction among thyroid-specific transcription factors: Pax8 regulates the activity of Hex promoter.
The transcription factor Hex is expressed in the thyroid follicular cells (TFC) and in several other cell types. In TFC, Hex contributes to the control of the tissue-specific gene expression. By means of RT-PCR assays we found a correlation between the Hex and Pax8 (a different tissue-specific transcription factor, expressed in TFC) mRNA levels in normal and neoplastic thyroid tissues. This finding suggested the presence of a functional correlation between the two transcription factors. Therefore, we tested whether Pax8 regulates the transcriptional activity of Hex promoter. Indeed, by using cotransfection experiments in non-thyroidal cells, we show that increasing doses of Pax8 expression vector elicited a dose-dependent increase of the transcriptional activity of Hex promoter. Accordingly, gel-retardation assays indicated that in the Hex promoter are present several Pax8 binding sites. The Pax8 activating effect on Hex promoter was further increased by the contemporary presence of Hex protein. In fact, cotransfection of both Hex and Pax8 expression vectors doubled the transcriptional activity of Hex promoter with respect to the condition in which the Pax8 expression vector only was transfected. In addition, we show that also the transcriptional cofactor APE/Ref-1 cooperated with Pax8 for upregulation of Hex promoter activity. These findings, together with other published data, suggest that a network of functional interactions between transcriptional regulators is present in TFC.
Puppin
Cinzia
C
Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, Piazzale Kolbe 1, 33100 Udine, Italy.
Presta
Ivan
I
D'Elia
Angela V
AV
Tell
Gianluca
G
Arturi
Franco
F
Russo
Diego
D
Filetti
Sebastiano
S
Damante
Giuseppe
G
D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009928:Organ Specificity; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic / Q000235:genetics*; D023302:Protein Footprinting; D012333:RNA, Messenger / Q000032:analysis; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; C078492:HHEX protein, human; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors