Mobile DNA elements play a major role in genome plasticity and other evolutionary processes, an insight gained primarily through the study of transposons and retrotransposons (generally approximately 1000 nt or longer). These elements spawn smaller parasitic versions (generally >100 nt) that propagate through proteins encoded by the full elements. Highly repeated sequences smaller than 100 nt have been described, but they are either nonmobile or their origins are not known. We have surveyed the genome of the multicellular cyanobacterium, Nostoc punctiforme, and its relatives for small dispersed repeat (SDR) sequences and have identified eight families in the range of from 21 to 27 nucleotides. Three of the families (SDR4, SDR5, and SDR6), despite little sequence similarity, share a common predicted secondary structure, a conclusion supported by patterns of compensatory mutations. The SDR elements are found in a diverse set of contexts, often embedded within tandemly repeated heptameric sequences or within minitransposons. One element (SDR5) is found exclusively within instances of an octamer, HIP1, that is highly over-represented in the genomes of many cyanobacteria. Two elements (SDR1 and SDR4) often are found within copies of themselves, producing complex nested insertions. An analysis of SDR elements within cyanobacterial genomes indicate that they are essentially confined to a coherent subgroup. The evidence indicates that some of the SDR elements, probably working through RNA intermediates, have been mobile in recent evolutionary time, making them perhaps the smallest known mobile elements.

译文

移动DNA元件在基因组可塑性和其他进化过程中起主要作用,这主要是通过研究转座子和反转录转座子 (通常约1000 nt或更长) 而获得的见解。这些元素产生较小的寄生版本 (通常> 100 nt),其通过由完整元素编码的蛋白质传播。已经描述了小于100 nt的高度重复序列,但是它们不是可移动的,或者它们的起源是未知的。我们已经调查了多细胞蓝细菌Nostoc punctiforme的基因组及其亲属的小分散重复序列 (SDR) 序列,并确定了21至27个核苷酸范围内的8个家族。尽管序列相似性很小,但三个家族 (SDR4,SDR5和SDR6) 具有共同的预测二级结构,这一结论得到了代偿性突变模式的支持。SDR元素存在于多种环境中,通常嵌入在连续重复的七聚体序列中或在微型子中。仅在八聚体HIP1的实例中发现了一种元素 (SDR5),该元素在许多蓝细菌的基因组中高度代表。在它们的副本中通常会发现两个元素 (SDR1和SDR4),从而产生复杂的嵌套插入。对蓝细菌基因组中SDR元素的分析表明,它们基本上局限于一个相干的亚组。证据表明,某些SDR元素 (可能通过RNA中间体起作用) 在最近的进化时间内已经移动,这使它们成为已知最小的移动元素。

+1
+2
100研值 100研值 ¥99课程
检索文献一次
下载文献一次

去下载>

成功解锁2个技能,为你点赞

《SCI写作十大必备语法》
解决你的SCI语法难题!

技能熟练度+1

视频课《玩转文献检索》
让你成为检索达人!

恭喜完成新手挑战

手机微信扫一扫,添加好友领取

免费领《Endnote文献管理工具+教程》

微信扫码, 免费领取

手机登录

获取验证码
登录