Nature. 1979 May 31;279(5712):448-50. doi: 10.1038/279448a0.
CHANGES in transcriptional activity at defined loci are often correlated with significant local structural changes in the genome(1), and in polytene chromosomes, such changes are thought to be associated with compositional or conformational changes in the protein complement at these particular bands(2,3). Thus, various studies on Balfoiani rings and specific 'puffs' in such chromosomes are useful for elucidating the role of defined chromosomal components in both chromosome structure and gene activity. Such studies require specific probes which will allow in situ localisation of a chromosomal component during the various stages of puffing. Antibodies specific to purified histone fractions(4-7), HMG proteins(8), RNA polymerase(9) and non-histone protein subfractions(10) have been used in studies on chromatin and chromosome structure. We reported previously that concanavalin A (Con A) specifically binds to three types of non-histone proteins present in chromatin purified from rat liver nuclei and suggested that derivatives of Con A might serve as specific probes to study the in situ organisation of these non-histone proteins(11). We have now reacted fluorescein-labelled Con A with polytene chromosomes isolated from different developmental stages of Chironomus thummi and visualised the location of the bound Con A by fluorescence microscopy. We observed that the fluorescent lectin, which has an affinity for glucose- and mannose-containing molecules, specifically bound to the transcriptionally active regions of chromosome IV. The extent of binding of Con A to the Balbiani rings present in regions b and c of chromosome IV is proportional to the size of the respective ring. Our results indicate that glucose- or mannose-containing molecules are present in these Balbiani rings and that the availability of these sugars to interact with Con A can be correlated with the developmental stage of a puff. We suggest that lectins can be useful cytological tools with which to study the in situ organisation of defined chromosomal components during various functional states of the genome.
在特定基因座的转录活性的变化通常与基因组中显著的局部结构变化相关（1），并且在多线染色体中，这些变化被认为与这些特定带的蛋白质组成或构象变化有关（2,3）。因此，关于 Balfoiani 环和此类染色体中特定“膨胀”的各种研究对于阐明特定染色体成分在染色体结构和基因活性中的作用是有用的。此类研究需要特定的探针，这些探针将允许在膨胀的各个阶段对染色体成分进行原位定位。针对纯化组蛋白分数（4-7）、HMG 蛋白（8）、RNA 聚合酶（9）和非组蛋白亚分数（10）的抗体已用于染色质和染色体结构的研究。我们之前报道过，刀豆球蛋白 A（Con A）特异性结合从大鼠肝核中纯化的染色质中存在的三种类型的非组蛋白，并且认为 Con A 的衍生物可能作为研究这些非组蛋白原位组织的特异性探针（11）。我们现在已经用荧光素标记的 Con A 与来自不同发育阶段的摇蚊多线染色体反应，并通过荧光显微镜观察结合的 Con A 的位置。我们观察到，该荧光凝集素与葡萄糖和甘露糖含有分子具有亲和力，特异性结合到染色体 IV 的转录活性区域。Con A 与染色体 IV 的区域 b 和 c 中存在的 Balbiani 环的结合程度与相应环的大小成正比。我们的结果表明，这些 Balbiani 环中存在含有葡萄糖或甘露糖的分子，并且这些糖与 Con A 相互作用的可用性可以与一个膨胀的发育阶段相关。我们认为凝集素可以成为有用的细胞学工具，用于研究基因组各种功能状态下特定染色体成分的原位组织。
