SINE extinction preceded LINE extinction in sigmodontine rodents: implications for retrotranspositional dynamics and mechanisms

Short Interspersed Nuclear Elements, or SINEs, retrotranspose despite lacking protein-coding capability. It has been proposed that SINEs utilize enzymes produced in trans by Long Interspersed Nuclear Elements, or LINEs. Strong support for this hypothesis is found in LINE and SINE pairs that share sequence homology; however, LINEs and SINEs in primates and rodents are only linked by an insertion site motif. We have now profiled L1 LINE and B1 SINE activity in 24 rodent species including candidate taxa for the first documented L1 extinction. As expected, there was no evidence for recent activity of B1s in species that also lack L1 activity. However, B1 silencing appears to have preceded L1 extinction, since B1 activity is also lacking in the genus most closely related to those lacking active L1s despite the presence of active L1s in this genus. A second genus with active L1s but inactive B1s was also identified.     

植物基因组中的非LTR反转录转座子SINEs和LINEs

反转录转座子是基因组进化的推动者之一。分为LTR和非LTR两种类型。前者是真核基因组的主要组分,结构和转座方式与逆转录病毒类似。后者是最初发现于动物基因组新近发现在植物基因组中也广泛存在的新型重复序列,包括LINEs(long interspersed nuclear elements)和SINEs(short interspersed nuclear elements)两个亚型。它们大多因自身或受宿主基因组的调控而失去转座活性。其转座机理目前还不十分清楚,推测LINEs可以自主转座,SINEs依赖其他转座子被动转座。种系分析认为LINEs可能是最古老的反转录转座子,SINEs的起源未知。文章对以上内容进行了归纳和讨论。