Krayev A S, Markusheva T V, Kramerov D A, Ryskov A P, Skryabin K G, Bayev A A, Georgiev G P
Nucleic Acids Res. 1982 Dec 11;10(23):7461-75. doi: 10.1093/nar/10.23.7461.
Mouse genome contains two major families of short interspersed repeats in more than 10(5) copies scattered throughout the whole genome. They are referred to as B1 and B2 sequences since they were first isolated from the genome library by means of a dsRNA-B probe /1/. In this work, two copies of the B2 family were sequenced and compared with the previously sequenced B1 repeat /2/. A B2 ubiquitous repeat is ca. 190 bp long. The members of the family deviate in 3-5% of nucleotides from the consensus sequence. B2 contains regions of homology to the RNA polymerase III split promoter and to 4.5S snRNA I. Both B1 and B2 contain regions which resemble junctions between exons and introns. In contrast to B1, B2 does not contain apparent homologies to papova viral replication origins and a human Alu sequence. One side of the B2 repeat is represented by a very AT-rich sequence (ca. 30 bp long) followed with an oligo (dA) stretch 10-15 nucleotides long. This region of the repeat is the most variable one. The whole unit is flanked with 15-16 bp direct repeats different in sequenced copies of B2. The same is true of some copies of the B1 family. The properties of B1 and B2 repeats suggest that they may represent a novel class of transposon-like elements in eukaryotic genome. A possible role of B-type repeats in genome reorganization, DNA replication and pre-mRNA processing is discussed.
小鼠基因组包含两个主要的短散在重复序列家族，超过10⁵个拷贝散布于整个基因组中。它们被称为B1和B2序列，因为它们最初是通过双链RNA - B探针从基因组文库中分离出来的/1/。在这项工作中，对B2家族的两个拷贝进行了测序，并与先前测序的B1重复序列进行了比较/2/。一个普遍存在的B2重复序列约190 bp长。该家族成员与共有序列在3% - 5%的核苷酸上存在差异。B2包含与RNA聚合酶III分裂启动子和4.5S小核仁RNA I的同源区域。B1和B2都包含类似于外显子和内含子之间连接的区域。与B1不同，B2与乳头瘤病毒复制起点和人类Alu序列没有明显的同源性。B2重复序列的一侧由一个富含AT的序列（约30 bp长）代表，后面跟着一段10 - 15个核苷酸长的寡聚（dA）序列。该重复序列的这一区域是最可变的。整个单元两侧是15 - 16 bp的直接重复序列，在B2的测序拷贝中有所不同。B1家族的一些拷贝也是如此。B1和B2重复序列的特性表明它们可能代表真核基因组中一类新型的转座子样元件。讨论了B型重复序列在基因组重组、DNA复制和前体mRNA加工中的可能作用。
