Percival-Smith A, Bondy J A
Department of Zoology, University of Western Ontario, London, Canada.
Dev Genet. 1999;24(3-4):336-44. doi: 10.1002/(SICI)1520-6408(1999)24:3/4<336::AID-DVG17>3.0.CO;2-R.
The murine HOXA-2 protein shares amino acid sequence similarity with Drosophila Proboscipedia (PB). In this paper, we test whether HOXA-2 and PB are functionally equivalent in Drosophila. In Drosophila, PB inhibits SCR activity required for larval T1 beard formation and adult tarsus formation and is required for maxillary palp and proboscis formation. HOXA-2 expressed from a heat-shock promoter weakly suppressed SCR activity required for T1 beard formation. But interestingly neither PB nor HOXA-2 expressed from a heat-shock promoter suppressed murine HOXA-5 activity, the murine SCR homologue, from inducing ectopic T1 beards in T2 and T3, indicating that HOXA-5 does not interact with PB. HOXA-2 activity expressed from the Tubulin alpha 1 promoter modified the pb null phenotype resulting in a proboscis-to-arista transformation, indicating that HOXA-2 was able to suppress SCR activity required for tarsus formation. However, HOXA-2 expressed from a Tubulin alpha 1 promoter was unable to direct maxillary palp determination when either ectopically expressed in the antenna or in the maxillary palp primordia of a pb null mutant. HOXA-2 was also unable to rescue pseudotrachea formation in a pb null mutant. These results indicate that the only activity that PB and HOXA-2 weakly share is the inhibition of SCR activity, and that murine HOXA-5 and Drosophila SCR do not share inhibition by PB activity.
小鼠HOXA-2蛋白与果蝇触须基因（PB）在氨基酸序列上具有相似性。在本文中，我们测试了HOXA-2和PB在果蝇中是否具有功能等效性。在果蝇中，PB抑制幼虫T1刚毛形成和成虫跗节形成所需的SCR活性，并且是上颚触须和喙形成所必需的。从热休克启动子表达的HOXA-2微弱地抑制了T1刚毛形成所需的SCR活性。但有趣的是，无论是从热休克启动子表达的PB还是HOXA-2，都不能抑制小鼠HOXA-5（小鼠SCR同源物）在T2和T3诱导异位T1刚毛的活性，这表明HOXA-5不与PB相互作用。从微管蛋白α1启动子表达的HOXA-2活性改变了pb基因敲除的表型，导致喙到触角芒转变，这表明HOXA-2能够抑制跗节形成所需的SCR活性。然而，当在pb基因敲除突变体的触角或上颚触须原基中异位表达时，从微管蛋白α1启动子表达的HOXA-2无法指导上颚触须的确定。HOXA-2也无法挽救pb基因敲除突变体中的假气管形成。这些结果表明，PB和HOXA-2微弱共享的唯一活性是对SCR活性的抑制，并且小鼠HOXA-5和果蝇SCR不共享PB活性的抑制作用。
