Maggini F, Cremonini R, Zolfino C, Tucci G F, D'Ovidio R, Delre V, DePace C, Scarascia Mugnozza G T, Cionini P G
Dipartimento di Agrobiologia e Agrochimica, Università della Tuscia, Viterbo, Italy.
Chromosoma. 1991 May;100(4):229-34. doi: 10.1007/BF00344156.
Subrepeating sequences of 325 bp found in the ribosomal intergenic spacer (IGS) of Vicia faba and responsible for variations in the length of the polycistronic units for rRNA were isolated and used as probes for in situ hybridization. Hybridization occurs at many regions of the metaphase chromosomes besides those bearing rRNA genes, namely chromosome ends and all the heterochromatic regions revealed by enhanced fluorescence after quinacrine staining. The DNA homologous to the 325 bp repeats that does not reside in the IGS was isolated, cloned and sequenced. It is composed of tandemly arranged 336 bp elements, each comprising two highly related 168 bp sequences. This structure is very similar to that of the IGS repeats and ca. 75% nucleotide sequence identity can be observed between these and the 168 bp doublets. The most obvious difference lies in the deletion, in the former, of a 14 bp segment from one of the two related sequences. It is hypothesized that the IGS repeats are derived from the 336 bp elements and have been transposed to ribosomal cistrons from other genome fractions. The possible relations between these sequences and others with similar structural features found in other species are discussed.
在蚕豆核糖体基因间隔区（IGS）中发现的325 bp亚重复序列，其负责rRNA多顺反子单元长度的变化，被分离出来并用作原位杂交的探针。除了携带rRNA基因的区域外，中期染色体的许多区域都会发生杂交，即染色体末端以及喹吖因染色后荧光增强所显示的所有异染色质区域。与不在IGS中的325 bp重复序列同源的DNA被分离、克隆并测序。它由串联排列的336 bp元件组成，每个元件包含两个高度相关的168 bp序列。这种结构与IGS重复序列的结构非常相似，并且在这些序列与168 bp双联体之间可以观察到约75%的核苷酸序列同一性。最明显的差异在于，在前者中两个相关序列之一缺失了一个14 bp的片段。据推测，IGS重复序列源自336 bp元件，并已从其他基因组片段转座到核糖体顺反子中。还讨论了这些序列与在其他物种中发现的具有类似结构特征的其他序列之间的可能关系。
