Nucleic Acids Research, 1991, Vol. 19, No. 5 1015-1019
© 1991
MOLECULAR BIOLOGY |
A sequence dimorphism in a conserved domain of human 28S rRNA. Uneven distribution of variant genes among individuals. Differential expression in HeLa cells
Centre de Recherche de Biochimie et de Génétique Cellulaires du Centre National de la Recherche Scientifique, Université Paul-Sabatier 118 route de Narbonne, 31062 Toulouse Cédex, France
* To whom correspondence should be addressed
Received December 31, 1990. Accepted February 4, 1991.
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.
+Permanent address: Biotechnology Research Center, Zhongshan University, Guangzhou 510275, China.