The Homothorax homeoprotein activates the nuclear localization of another homeoprotein, Extradenticle, and suppresses eye development in Drosophila
- Chi-Yun Pai,
- Tung-Sheng Kuo,
- Thomas J. Jaw,
- Estee Kurant,
- Cheng-Tse Chen,
- Dmitri A. Bessarab,
- Adi Salzberg, and
- Y. Henry Sun
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 11529, Taiwan, Republic of China, Institute of Life Science, National Sun Yat-Sen University, Kaohsiung, Taiwan; Institute of Genetics, National Yang-Ming University, Shipai, Taipei, Taiwan, Unit of Genetics, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel
Abstract
The Extradenticle (Exd) protein in Drosophila acts as a cofactor to homeotic proteins. Its nuclear localization is regulated. We report the cloning of the Drosophila homothorax(hth) gene, a homolog of the mouse Meis1 proto-oncogene that has a homeobox related to that of exd. Comparison with Meis1 finds two regions of high homology: a novel MH domain and the homeodomain. In imaginal discs, hth expression coincides with nuclear Exd. hth and exd also have virtually identical, mutant clonal phenotypes in adults. These results suggest thathth and exd function in the same pathway. We show thathth acts upstream of exd and is required and sufficient for Exd protein nuclear localization. We also show that hth andexd are both negative regulators of eye development; their mutant clones caused ectopic eye formation. Targeted expression ofhth, but not of exd, in the eye disc abolished eye development completely. We suggest that hth acts withexd to delimit the eye field and prevent inappropriate eye development.
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Footnotes
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↵Corresponding author.
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E-MAIL mbyhsun{at}ccvax.sinica.edu.tw; FAX (886-2) 2782-6085.
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- Received October 16, 1997.
- Accepted December 2, 1997.
- Cold Spring Harbor Laboratory Press
