Kramerov D A, Ryskov A P, Georgiev G P
Biochim Biophys Acta. 1977 Apr 4;475(3):461-75. doi: 10.1016/0005-2787(77)90062-4.
High molecular weight nuclear pre-messenger RNA (pre-mRNA or hnRNA) isolated from Ehrlich ascites carcinoma cells contains besides moderately long (100--200 base pairs) snap-back double-stranded structures, also longer double-stranded structure containing at least 300--800 base pairs. Their double-stranded nature was proved by Cs2SO4 gradient centrifugation. Very long double-stranded sequences are not able to snap-back after RNA melting. While the moderately long double-stranded RNA (dsRNA) is renatured at C0t1/2 approximately equal to 5-10(-4), the very long dsRNA shows a higher complexity (C0t1/2 approximately equal to 2-10(-2). They also hybridize to less reiterated class of DNA than moderately long dsRNA. Two classes of dsRNA are represented by different sequences as followed from cross-renaturation experiments. Very long dsRNA forms stable hybrids with 20% of total poly(A)+mRNA of cytoplasm. The properties of different classes of ds structures present in nuclear pre-mRNA are compared and their possible nature is discussed. The presence of very long dsRNA may reflect either the symmetric transcription of structural genes, or the transcription from those DNA sequences which are complementary to each other but located in different parts of the genome.
从艾氏腹水癌细胞中分离出的高分子量核内前体信使核糖核酸（前体mRNA或核内不均一RNA），除了含有中等长度（100 - 200个碱基对）的回折双链结构外，还含有至少300 - 800个碱基对的更长双链结构。通过硫酸铯梯度离心证明了它们的双链性质。RNA解链后，非常长的双链序列无法回折。中等长度的双链RNA（dsRNA）在C0t1/2约等于5 - 10（-4）时复性，而非常长的dsRNA显示出更高的复杂度（C0t1/2约等于2 - 10（-2））。与中等长度的dsRNA相比，它们与重复程度较低的DNA类别的杂交能力也较弱。从交叉复性实验可以看出，两类dsRNA由不同序列代表。非常长的dsRNA与细胞质中20%的总poly(A)+mRNA形成稳定杂交体。对核内前体mRNA中存在的不同类别ds结构的性质进行了比较，并讨论了它们可能的性质。非常长的dsRNA的存在可能反映了结构基因的对称转录，或者是从基因组中彼此互补但位于不同部位的DNA序列转录而来。
