Soriano P, Meunier-Rotival M, Bernardi G
Proc Natl Acad Sci U S A. 1983 Apr;80(7):1816-20. doi: 10.1073/pnas.80.7.1816.
We investigated the genomic distribution of mouse and human repeated sequences by assessing their relative amounts in the four major components into which these genomes can be resolved by density gradient centrifugation techniques. These components are families of fragments that account for most or all of main-band DNAs, range in dG + dC content from 37% to 49%, and are derived by preparative breakage from long DNA segments (greater than 300 kb) of fairly homogeneous composition, the isochores. The results indicate that the short repeats of the B1 family of mouse and of the Alu I family of man are most frequent in the heavy components, whereas the long repeats of the BamHI family of mouse and of the Kpn I family of man are mainly present in the two light components. These results show that the genomic distribution of repeated sequences is nonuniform and conserved in two mammalian species. In addition, we observed that the base composition of two classes of repeats (60% dG + dC for short repeats; 39% dG + dC for long repeats) is correlated with the composition of the major components in which they are embedded. Finally, we obtained evidence that not only the short repeats but also the long repeats are transcribed, these transcripts having been found in mouse poly(A)+ mRNA.
我们通过评估小鼠和人类重复序列在密度梯度离心技术可将这些基因组解析成的四个主要组分中的相对含量，来研究它们的基因组分布。这些组分是片段家族，它们占主带DNA的大部分或全部，dG + dC含量在37%至49%之间，并且是通过制备性断裂从组成相当均匀的长DNA片段（大于300 kb）即等密度区带衍生而来。结果表明，小鼠B1家族和人类Alu I家族的短重复序列在重组分中最为常见，而小鼠BamHI家族和人类Kpn I家族的长重复序列主要存在于两个轻组分中。这些结果表明，重复序列的基因组分布在两种哺乳动物中是不均匀且保守的。此外，我们观察到两类重复序列的碱基组成（短重复序列为60% dG + dC；长重复序列为39% dG + dC）与其所嵌入的主要组分的组成相关。最后，我们获得的证据表明，不仅短重复序列，长重复序列也会被转录，这些转录本已在小鼠多聚腺苷酸加尾mRNA中被发现。
