Langeland J A, Carroll S B
Howard Hughes Medical Institute, Laboratory Of Molecular Biology, University of Wisconsin, Madison 53706.
Development. 1993 Feb;117(2):585-96. doi: 10.1242/dev.117.2.585.
The hairy (h) gene is one of two pair-rule loci whose striped expression is directly regulated by combinations of gap proteins acting through discrete upstream regulatory fragments, which span several kilobases. We have undertaken a comparative study of the molecular biology of h pair-rule expression in order to identify conserved elements in this complex regulatory system, which should provide important clues concerning the mechanism of stripe formation. A molecular comparison of the h locus in Drosophila virilis and Drosophila melanogaster reveals a conserved overall arrangement of the upstream regulatory elements that control individual pair-rule stripes. We demonstrate that upstream fragments from D. virilis will direct the proper expression of stripes in D. melanogaster, indicating that these are true functional homologs of the stripe-producing D. melanogaster regulatory elements, and that the network of trans-acting proteins that act upon these regulatory elements is highly conserved. We also demonstrate that the spatial relationships between specific h stripes and selected gap proteins are highly conserved. We find several tracts of extensive nucleotide sequence conservation within homologous stripe-specific regulatory fragments, which have facilitated the identification of functional subelements within the D. melanogaster regulatory fragment for h stripe 5. Some of the conserved nucleotide tracts within this regulatory fragment contain consensus binding sites for potential trans-regulatory (gap and other) proteins, while many appear devoid of known binding sites. This comparative approach, coupled with the analysis of reporter gene expression in gap mutant embryos suggests that the Kr and gt proteins establish the anterior and posterior borders of h stripe 5, respectively, through spatial repression. Other, as yet unidentified, proteins are certain to play a role in stripe activation, presumably acting through other conserved sequence tracts.
毛（h）基因是两个成对规则基因座之一，其条纹状表达由通过离散的上游调控片段起作用的间隙蛋白组合直接调控，这些片段跨越数千个碱基对。我们对h成对规则表达的分子生物学进行了比较研究，以确定这个复杂调控系统中的保守元件，这应该能为条纹形成机制提供重要线索。对粗壮果蝇和黑腹果蝇中h基因座的分子比较揭示了控制单个成对规则条纹的上游调控元件的整体保守排列。我们证明，来自粗壮果蝇的上游片段将指导黑腹果蝇中条纹的正确表达，这表明这些是产生条纹的黑腹果蝇调控元件的真正功能同源物，并且作用于这些调控元件的反式作用蛋白网络高度保守。我们还证明了特定h条纹与选定间隙蛋白之间的空间关系高度保守。我们在同源的条纹特异性调控片段中发现了几处广泛的核苷酸序列保守区域，这有助于鉴定黑腹果蝇h条纹5调控片段内的功能亚元件。该调控片段内的一些保守核苷酸区域含有潜在反式调控（间隙及其他）蛋白的共有结合位点，而许多区域似乎没有已知的结合位点。这种比较方法，再加上对间隙突变胚胎中报告基因表达的分析表明，Kr和gt蛋白分别通过空间抑制作用确定了h条纹5的前后边界。其他尚未确定的蛋白肯定在条纹激活中起作用，大概是通过其他保守序列区域发挥作用。
