Garkavtsev I V, Tsvetkova T G, Yegolina N A, Gudkov A V
Institute of Medical Genetics, Academy of Medical Sciences, Moscow, USSR.
Hum Genet. 1988 Dec;81(1):31-7. doi: 10.1007/BF00283725.
Human rRNA genes contain variable regions, one of which is located in nontranscribed spacers (NTSs) closely downstream from the 3'-end of the transcribed region. This polymorphism may be detected by means of blot hybridization analysis as a set of distinct restriction fragments corresponding to this part of the rRNA genes. We have analyzed DNA of 51 individuals and found eight structural NTS variants of this region; two of these were common to all individuals analyzed, and six others were found in different combinations and with different frequencies. The copy number of each variant also differed but was not less than 10-20 copies per cell. The analysis of DNA isolated from leukocytes of the members of 11 families indicated that some of the structural variants (of the NTS region) are inherited as a single Mendelian locus. We propose that rRNA genes that belong to one particular structural variant form clusters on separate chromosomes. To test this proposition, we developed a combined method, including AgNO3-staining of chromosomes, in situ hybridization, and DNA analysis with methylation-sensitive restrictases, and used it for study of persons who had methylated rRNA genes located on AgNO3-negative nucleolar organizers. It was found that in three of four cases methylated genes really belonged to one structural variant. This approach may be used for detailed localization of separate classes of NTS structural variants of human rRNA genes.
人类rRNA基因包含可变区，其中一个位于转录区3'端下游紧邻的非转录间隔区（NTSs）。这种多态性可通过印迹杂交分析检测到，表现为一组与rRNA基因这一部分相对应的独特限制性片段。我们分析了51个人的DNA，发现该区域有8种结构性NTS变体；其中两种对所有分析个体来说是常见的，另外六种以不同组合和频率出现。每个变体的拷贝数也不同，但每个细胞不少于10 - 20个拷贝。对11个家庭成员白细胞中分离出的DNA进行分析表明，一些（NTS区域的）结构性变体作为单一孟德尔位点遗传。我们提出，属于一个特定结构变体的rRNA基因在不同染色体上形成簇。为了验证这一观点，我们开发了一种联合方法，包括染色体硝酸银染色、原位杂交以及用甲基化敏感限制酶进行DNA分析，并将其用于研究位于硝酸银阴性核仁组织者上的甲基化rRNA基因的人。结果发现，在四例中有三例甲基化基因确实属于一个结构变体。这种方法可用于人类rRNA基因NTS结构变体不同类别的详细定位。
