C-Myb acts as transcriptional activator of the quail PAX6 (PAX-QNR) promoter through two different mechanisms.
To understand the regulation of the Pax-6 gene, which plays an important role in eye development, we have characterized the promoter region of the quail Pax-6(Pax-QNR) gene. In addition to TATA and CAAT boxes, sequence analysis revealed several putative cis-regulatory elements among which three myb-responsive elements (MRE). C-myb encodes a nuclear, DNA-binding phosphoprotein that functions as transcriptional regulator. Co-transfection in quail embryo cells of the Pax-QNR/pax-6 promoter with a vector expressing the 75 kDa c-myb protein resulted in an increase in Pax-QNR promoter activity. By footprinting experiments we identified multiple binding sites for the myb protein within the promoter region. Protein containing the myb DNA-binding domain fused to the VP16-transactivation domain was fully efficient in Pax-QNR promoter transactivation, demonstrating that myb can transactivate through a direct binding on DNA. However, a myb truncated protein devoid of DNA-binding domain was also able to transactivate the Pax-QNR promoter. These results show that this promoter can be transactivated by the myb protein directly as well as indirectly. Finally we show by in situ hybridization that c-myb is strongly expressed in the developing neuroretina, simultaneously with Pax-QNR. These observations suggest that the c-myb protein may be a regulator of Pax-QNR/pax-6.
Laboratoire de Differenciation Cellulaire et Moléculaire, CNRS EP56 Institut Pasteur, Lille, France.
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Plaza
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Turque
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Dozier
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Bailly
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Saule
D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D005136:Eye Proteins; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009857:Oncogenes; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic; D011784:Quail / Q000196:embryology / Q000235:genetics*; D012097:Repressor Proteins; D012160:Retina / Q000196:embryology; D016385:TATA Box; D015534:Trans-Activators; D014162:Transfection
D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D015534:Trans-Activators