Avery R J, Midgley J E, Pigott G H
Biochem J. 1969 Nov;115(3):395-403. doi: 10.1042/bj1150395.
From analyses of the hybridization of Escherichia coli rRNA (ribosomal RNA) to homologous denatured DNA, the following conclusions were drawn. (1) When a fixed amount of DNA was hybridized with increasing amounts of RNA, only 0.35+/-0.02% of E. coli DNA was capable of binding (16s+23s) rRNA. Although preparations of 16s and 23s rRNA were virtually free from cross-contamination, the hybridization curves for purified 16s or 23s rRNA were almost identical with that of the parent specimen containing 1 weight unit of 16s rRNA mixed with 2 weight units of 23s rRNA. The 16s and 23s rRNA also competed effectively for the same specific DNA sites. It appears that these RNA species each possess all hybridizing species typical of the parent (16s+23s) rRNA specimen, though probably in different relative amounts. (2) By using hybridization-efficiency analysis of DNA-RNA hybridization curves (Avery & Midgley, 1969) it was found that (a) 0.45% of the DNA would hybridize total rRNA and (b) when so little RNA was added to unit weight of DNA that the DNA sites were not saturated, only 70-75% of the input RNA would form hybrids. The reasons for the discrepancy between the results obtained by the two alternative analytical approaches were discussed. (3) For either 16s or 23s rRNA, hybridization analysis indicated that two principal weight fractions of rRNA may exist, hybridizing to two distinct groups of DNA sites. However, these groups seem to be incompletely divided between the 16s and 23s fractions. Analysis suggested that (a) 85% of the 16s rRNA was hybridized to about half the DNA that specifically binds rRNA (0.23% of the total DNA). (b) 70% of the 23s rRNA hybridized to a further 0.23% of the DNA and (c) the minor fraction (15%) of 16s rRNA may be competitive with the major fraction (70%) of 23s rRNA. Conversely, the minor fraction (30%) of the 23s rRNA may compete with the major fraction (85%) of 16s rRNA. Models were proposed to explain the apparent lack of segregation of distinct RNA species in the two subfractions of rRNA. (4) If protein synthesis and ribosome maturation were inhibited in cells of an RC(rel) mutant, E. coli W 1665, by depriving them of an amino acid (methionine) essential for growth, the inhibition had no discernible effect on the relative rates of synthesis of rRNA species. The rRNA that accumulates in RC(rel) strains of E. coli after amino acid deprivation is apparently identical in its content of RNA species with that of the pre-existing mature RNA in the ribosomes. On the other hand, the messenger RNA is stabilized, and accumulates as about 15% of the RNA formed after withdrawal of the amino acid.
通过对大肠杆菌核糖体RNA（rRNA）与同源变性DNA杂交的分析，得出了以下结论。（1）当用固定量的DNA与不断增加量的RNA杂交时，只有0.35±0.02%的大肠杆菌DNA能够结合（16s + 23s）rRNA。尽管16s和23s rRNA的制备几乎没有交叉污染，但纯化的16s或23s rRNA的杂交曲线与含有1重量单位16s rRNA和2重量单位23s rRNA混合的母本样本的杂交曲线几乎相同。16s和23s rRNA也能有效地竞争相同的特定DNA位点。看来这些RNA种类各自拥有母本（16s + 23s）rRNA样本的所有典型杂交种类，尽管其相对含量可能不同。（2）通过使用DNA - RNA杂交曲线的杂交效率分析（Avery和Midgley，1969）发现：（a）0.45%的DNA能与总rRNA杂交；（b）当向单位重量的DNA中加入如此少量的RNA以至于DNA位点未饱和时，只有70 - 75%的输入RNA会形成杂交体。讨论了两种不同分析方法所得结果存在差异的原因。（3）对于16s或23s rRNA，杂交分析表明rRNA可能存在两个主要的重量组分，它们与两组不同的DNA位点杂交。然而，这些组在16s和23s组分之间似乎没有完全分开。分析表明：（a）85%的16s rRNA与特异性结合rRNA的大约一半DNA杂交（占总DNA的0.23%）。（b）70%的23s rRNA与另外0.23%的DNA杂交，并且（c）16s rRNA的小部分（15%）可能与23s rRNA的大部分（70%）竞争。相反，23s rRNA的小部分（30%）可能与16s rRNA的大部分（85%）竞争。提出了模型来解释rRNA的两个亚组分中不同RNA种类明显缺乏分离的现象。（4）如果通过剥夺生长必需氨基酸（甲硫氨酸）来抑制RC(rel)突变体大肠杆菌W 1665细胞中的蛋白质合成和核糖体成熟，这种抑制对rRNA种类的相对合成速率没有明显影响。在大肠杆菌的RC(rel)菌株中，氨基酸剥夺后积累的rRNA在其RNA种类含量上显然与核糖体中预先存在的成熟RNA相同。另一方面，信使RNA被稳定下来，并作为氨基酸去除后形成的RNA的约15%积累起来。
