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PMID:10206974
| Citation |
Amendt, BA, Sutherland, LB and Russo, AF (1999) Transcriptional antagonism between Hmx1 and Nkx2.5 for a shared DNA-binding site. J. Biol. Chem. 274:11635-42 |
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| Abstract |
The recently described Hmx family of homeodomain proteins is predominately expressed in discrete regions of developing sensory tissues. In this report, we have identified the preferred DNA-binding site of the murine Hmx3 homeodomain protein by the selection and amplification binding (SAAB) technique. The consensus Hmx-binding site contained the sequence 5'-CAAGTG-3', which differs from the 5'-TAAT-3' motif commonly associated with homeodomain proteins. Instead, the Hmx consensus is similar to the 5'-CAAGTG-3'-binding sites of Nkx2.1 and Nkx2.5 homeodomain proteins. Based on mutation studies, both the 5'-CAAG-3' core and the 3'-TG dinucleotide are required for high affinity binding by Hmx3 and the homologous Hmx1 protein. A critical determinant of this specificity is the glutamine at position 50 in the third helix of the Hmx homeodomain. Hmx1 binds to the 5'-CAAGTG-3' element with an apparent dissociation constant of 20 nM. Unexpectedly, the human Hmx1 protein specifically repressed transcription from a luciferase reporter gene containing 3 copies of the 5'-CAAGTG-3' sequence. In contrast, the Nkx2.5 protein transactivated this luciferase reporter. Interestingly, co-expression of Hmx1 and Nkx2.5 attenuated each others activity, suggesting that genes containing the CAAGTG element can integrate signals from these proteins. Therefore, Hmx1 and Nkx2. 5 proteins bind a unique DNA sequence and act as transcriptional antagonists. |
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| Keywords |
Base Sequence; Binding Sites; DNA Primers; DNA-Binding Proteins/genetics; DNA-Binding Proteins/metabolism; Homeodomain Proteins/genetics; Homeodomain Proteins/metabolism; Mutation; Transcription Factors; Transcription, Genetic; Xenopus Proteins |
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Significance
Annotations
| Gene product | Qualifier | GO ID | GO term name | Evidence Code | with/from | Aspect | Notes | Status |
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See also
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