Noma K, Nakajima R, Ohtsubo H, Ohtsubo E
Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Genes Genet Syst. 1997 Jun;72(3):131-40. doi: 10.1266/ggs.72.131.
RIRE1 is a retrotransposon present in wild rice Oryza australiensis in an extraordinary number of copies, and only a portion of the LTR sequence has been determined previously. Here, we isolated and sequenced DNA segments of various portions of RIRE1, revealing that the sequences of LTR and the internal region were 1523 and 5277 bp in length, respectively. The internal region shows homology with the pol region in copia, a Drosophila retrotransposon, indicating that RIRE1 is a copia-like retrotransposon. The internal region of RIRE1 contained an open reading frame coding for genes, gag, pro, int, rt and rh, like copia and retroelements related to it. A clone screened from a library of the O. australiensis genomic DNA contained solo LTR, which was flanked by direct repeats of a 5-bp sequence. This suggests that RIRE1 generates a duplication of the target sequence of 5 bp upon retroposition. We observed that many RIRE1 members were nested by another RIRE1 member. This indicates that these RIRE1 members have received another RIRE1 to make an extraordinary number of copies in the O. australiensis genome without giving a deleterious effect on the growth of rice cells.
RIRE1是一种反转录转座子，在野生稻澳洲野生稻（Oryza australiensis）中以极多的拷贝数存在，此前仅确定了其长末端重复序列（LTR）的一部分。在此，我们分离并测序了RIRE1不同部分的DNA片段，发现LTR序列和内部区域的长度分别为1523和5277碱基对。内部区域与果蝇反转录转座子copia中的pol区域具有同源性，表明RIRE1是一种类似copia的反转录转座子。RIRE1的内部区域包含一个编码基因gag、pro、int、rt和rh的开放阅读框，类似于copia及其相关的反转元件。从澳洲野生稻基因组DNA文库中筛选出的一个克隆包含单独的LTR，其两侧是一个5碱基序列的直接重复序列。这表明RIRE1在反转录转座时会产生一个5碱基的靶序列重复。我们观察到许多RIRE1成员被另一个RIRE1成员嵌套。这表明这些RIRE1成员获得了另一个RIRE1，从而在澳洲野生稻基因组中产生了极多的拷贝，而对水稻细胞的生长没有产生有害影响。
