Retrotransposon BARE-1:: expression of encoded proteins and formation of virus-like particles in barley cells
Retrotransposon BARE-1:: expression of encoded proteins and formation of virus-like particles in barley cells
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DOI：
10.1046/j.1365-313x.1999.00616.x
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发表时间：
1999-11-01
期刊：
影响因子：
7.2
通讯作者：
Schulman, AH
中科院分区：
文献类型：
--
作者：
Jääskeläinen, M;Mykkänen, AH;Schulman, AH
逆转录转座子是植物基因组中普遍存在的主要组成部分，其基因组结构和编码的主要蛋白质具有典型的逆转录病毒样特征。然而，很少有直接证明是转录或反转录的。大麦 (Hordeum vulgare) 的 BARE-1 逆转录转座子家族非常普遍，转录活跃，并且包含高度保守的功能区域。 BARE-1 的插入位点在大麦基因组中具有高度多态性。在这里，我们展示了 BARE-1 被翻译，并且预测多蛋白的衣壳蛋白 (GAG) 和整合酶 (IN) 成分被加工成预期大小的多肽。一些 GAG 与 IN 和 BARE-1 cDNA 一起沉积为病毒样颗粒。逆转录酶活性也存在于含有 BARE-1 翻译产物的梯度级分中。在含有 BARE-1 成分的级分中也观察到了病毒样颗粒。因此，执行活性逆转录转座子生命周期所必需的 BARE-1 组件似乎存在于体内并进行组装。这表明翻译后机制可能正在发挥作用，通过不受限制的整合来防止基因组的快速膨胀。
Retrotransposons are ubiquitous and major components of plant genomes, and are characteristically retroviral-like in their genomic structure and in the major proteins encoded. Nevertheless, few have been directly demonstrated to be transcribed or reverse transcribed. The BARE-1 retrotransposon family of barley (Hordeum vulgare) is highly prevalent, actively transcribed, and contains well conserved functional regions. Insertion sites for BARE-1 are highly polymorphic in the barley genome. Here we show that BARE-1 is translated and the capsid protein (GAG) and integrase (IN) components of the predicted polyprotein are processed into polypeptides of expected size. Some of the GAG sediments as virus-like particles together with IN and with BARE-1 cDNA. Reverse transcriptase activity is also present in gradient fractions containing BARE-1 translation products. Virus-like particles have also been visualized in fractions containing BARE-1 components. Thus BARE-1 components necessary for carrying out the life cycle of an active retrotransposon appear to be present in vivo, and to assemble. This would suggest that post-translational mechanisms may be at work to prevent rapid genome inflation through unrestricted integration.