Tonnesen T, Engberg J, Leick V
Eur J Biochem. 1976 Apr 1;63(2):399-407. doi: 10.1111/j.1432-1033.1976.tb10241.x.
The amount and location of tRNA and 5-S rRNA genes in the macronucleus of Tetrahymena pyriformis GL was investigated by DNA-RNA hybridization. Hybridization of 32P-labelled tRNA in excess of unlabelled rRNA (25-S + 17-S + 5-S) showed that at saturation 0.021% of the macronuclear DNA was complementary to tRNA. Hybridization of 32P-labelled 5-S rRNA in excess of unlabelled 25-S + 17-S rRNA and tRNA showed a saturation value of 0.017%. In contrast to the 25-S + 17-S rRNA genes, which are found in DNA of high bouyant density, tRNA and 5-S rRNA genes were distributed evenly throughout the main peak observed when bulk macronuclear DNA was fractionated by density centrifugation in CsCl gradients. Sucrose gradient analyses of total macronuclear DNA showed that tRNA and 5-S rRNA genes were found in DNA of all size classes but a significant enrichment in the slowly sedimenting DNA fraction was observed. Saturation hybridization of 5-S rRNA to purified rDNA showed that rDNA did not contain any 5-S rRNA genes.
通过DNA - RNA杂交研究了梨形四膜虫GL大核中tRNA和5 - S rRNA基因的数量和定位。用过量未标记的rRNA（25 - S + 17 - S + 5 - S）杂交32P标记的tRNA，结果表明，饱和时0.021%的大核DNA与tRNA互补。用过量未标记的25 - S + 17 - S rRNA和tRNA杂交32P标记的5 - S rRNA，饱和值为0.017%。与在高浮力密度DNA中发现的25 - S + 17 - S rRNA基因不同，当在CsCl梯度中通过密度离心分离大量大核DNA时，tRNA和5 - S rRNA基因均匀分布在观察到的主峰中。对总大核DNA进行蔗糖梯度分析表明，在所有大小类别的DNA中都发现了tRNA和5 - S rRNA基因，但在沉降慢的DNA组分中观察到显著富集。5 - S rRNA与纯化的rDNA的饱和杂交表明，rDNA不包含任何5 - S rRNA基因。
