Coordinately expressed members of two chorion multi-gene families are clustered, alternating and divergently orientated
Coordinately expressed members of two chorion multi-gene families are clustered, alternating and divergently orientated
复制标题
两个绒毛膜多基因家族的协调表达成员呈聚集、交替和不同方向
作者：
C. Weldon Jones;F. C. Kafatos
蚕蛾的绒毛膜(蛋壳)由100多种不同的蛋白质组成。在绒毛膜发育的早、中、晚或极晚期(共持续2天)，单个成分以特征和重叠的序列合成1，2。蛋白质序列3，4表明属于A和B两个大小类别的成分分别由进化上同源的两个基因家族(多基因家族)编码。对家蚕mori5，6的遗传分析表明，绒毛膜基因紧密连锁在一条染色体上的三个簇中(n=28)。野桑蚕(Antheraea Polyphemus)绒毛膜总mRNA已被复制到双链cDNA中，并通过重组DNA程序进行克隆。通过详细的杂交和测序分析，已经筛选出许多不同的cDNA克隆，并鉴定为A和B多基因家族的成员。最大限度减少交叉杂交的严格条件允许使用这些克隆作为特定的探针。在许多情况下，我们知道在细胞质RNA7，8中可以找到克隆序列的蛋白质编码和发育时期。因此，我们现在可以使用这些克隆作为探针来确定已知发育特性和进化历史的基因在绒毛膜染色体区域内是如何排列的。我们在此报告了两个克隆的14kb染色体DNA片段，其中包含多个绒毛膜基因。在每个片段中，基因代表A和B两个家族，但只代表一个发育级别：一个片段只包含中期A和B基因，另一个片段只包含晚期A和B基因。在这两个片段中，两个家族的成员以交替的顺序和不同的方向排列。
The chorion (eggshell) of silkmoths consists of more than 100 distinct proteins. Individual components are synthesised in characteristic and overlapping sequence, at early, middle, late or very late developmental periods of choriogenesis (which lasts 2 days in total)1,2. Protein sequencing3,4 indicates that components which belong to two size classes, A and B, are encoded by two respective families of evolutionarily homologous genes (multi-gene families). Genetic analysis in Bombyx mori5,6 has shown that chorion genes are tightly linked in three clusters on a single chromosome (n = 28). Total chorion mRNA of the wild silkworm, Antheraea polyphemus, has been copied into double-stranded cDNA and cloned by recombinant DNA procedures7. Many distinct cDNA clones have been selected and identified as members of the A and B multi-gene families by detailed cross-hybridisation7 and sequencing8 analysis. Stringent conditions which minimise cross-hybridisation permit use of these clones as specific probes. In many cases, we know the protein encoded and the developmental period when the clone sequence can be found in cytoplasmic RNA7,8. Thus, we may now use these cDNA clones as probes to determine how genes of known developmental properties and evolutionary history are arranged within the chorion chromosomal region. We report here that two cloned, 14-kilobase chromosomal DNA segments contain multiple chorion genes. In each segment, the genes represent both A and B families, but only one developmental class: one segment contains only middle-period A and B genes and the other only late-period A and B genes. In both segments, members of the two families are arranged in alternating sequence and divergent orientation.