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Operator-constitutive mutations in a DNA sequence recognized by a yeast homeodomain
1Department of Microbiology and Immunology, University of California, San Francisco 94143.
The EMBO Journal
|May 15, 1994
Summary
Yeast alpha 2 homeodomain exhibits modest DNA-binding specificity, tolerating mutations in its recognition sequence. This relaxed specificity may facilitate the evolution of new regulatory circuits.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- Homeodomain proteins are crucial transcription regulators in development across diverse species.
- The DNA-binding specificity of homeodomains, especially when cooperating with other proteins, is not fully understood.
Purpose of the Study:
- To investigate the DNA-binding specificity of the yeast alpha 2 homeodomain.
- To determine how mutations in the recognition sequence affect alpha 2 homeodomain binding affinity and operator function.
Main Methods:
- In vivo and in vitro analysis of point mutations in the alpha 2 homeodomain recognition sequence.
- Measurement of homeodomain affinity with and without the helper protein MCM1.
- Assessment of operator function in vivo.
Main Results:
- Most recognition sequence mutations had minor effects on alpha 2 homeodomain affinity and operator function.
- This demonstrates the modest DNA-binding specificity of the alpha 2 homeodomain.
- This contrasts with highly specific bacterial and phage repressors.
Conclusions:
- The alpha 2 homeodomain's relaxed DNA-binding specificity is attributed to adaptable amino acid side chain interactions.
- This flexibility may enable rapid evolution of regulatory networks.
- Modest specificity is a key feature of homeodomain proteins for evolutionary adaptability.