Qu L H, Nicoloso M, Bachellerie J P
Centre de Recherche de Biochimie et de Génétique Cellulaires, Université Paul-Sabatier, Toulouse, France.
Nucleic Acids Res. 1991 Mar 11;19(5):1015-9. doi: 10.1093/nar/19.5.1015.
In humans, cellular 28S rRNA displays a sequence dimorphism within an evolutionarily conserved motif, with the presence, at position +60, of either a A (like the metazoan consensus) or a G. The relative abundance of the two forms of variant genes in the genome exhibit large differences among individuals. The two variant forms are generally represented in cellular 28S rRNA in proportion of their relative abundance in the genome, at least for leucocytes. However, in some cases, one form of variant may be markedly underexpressed as compared to the other. Thus, in HeLa cells, A-form genes contribute to only 1% of the cellular content in mature 28S rRNA although amounting to 15% of the ribosomal genes. The differential expression seems to result from different transcriptional activities rather than from differences in pre-rRNA processing efficiency or in stabilities of mature rRNAs. G-form ribosomal genes were not detected in other mammals, including chimpanzee, which suggests that the fixation of this variant type is a rather recent event in primate evolution.
在人类中，细胞28S rRNA在一个进化保守基序内呈现序列二态性，在+60位置存在一个A（类似后生动物共有序列）或一个G。基因组中两种变异基因形式的相对丰度在个体间存在很大差异。至少对于白细胞而言，这两种变异形式在细胞28S rRNA中的比例通常与其在基因组中的相对丰度成比例。然而，在某些情况下，一种变异形式可能与另一种相比明显低表达。因此，在HeLa细胞中，A形式基因在成熟28S rRNA的细胞含量中仅占1%，尽管其在核糖体基因中占15%。这种差异表达似乎是由不同的转录活性导致的，而不是由前体rRNA加工效率或成熟rRNA稳定性的差异导致的。在包括黑猩猩在内的其他哺乳动物中未检测到G形式的核糖体基因，这表明这种变异类型的固定在灵长类进化中是一个相当近期的事件。
