Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92697.
Department of Chemistry, University of California, Irvine, California 92697.
J Biol Chem. 2011 Dec 2;286(48):41286-41295. doi: 10.1074/jbc.M111.297283. Epub 2011 Oct 12.
Many non-long terminal repeat (non-LTR) retrotransposons lack internal promoters and are co-transcribed with their host genes. These transcripts need to be liberated before inserting into new loci. Using structure-based bioinformatics, we show that several classes of retrotransposons in phyla-spanning arthropods, nematodes, and chordates utilize self-cleaving ribozymes of the hepatitis delta virus (HDV) family for processing their 5' termini. Ribozyme-terminated retrotransposons include rDNA-specific R2, R4, and R6, telomere-specific SART, and Baggins and RTE. The self-scission of the R2 ribozyme is strongly modulated by the insertion site sequence in the rDNA, with the most common insertion sequences promoting faster processing. The ribozymes also promote translation initiation of downstream open reading frames in vitro and in vivo. In some organisms HDV-like and hammerhead ribozymes appear to be dedicated to processing long and short interspersed elements, respectively. HDV-like ribozymes serve several distinct functions in non-LTR retrotransposition, including 5' processing, translation initiation, and potentially trans-templating.
许多非长末端重复（non-LTR）逆转录转座子缺乏内部启动子，并且与它们的宿主基因共转录。这些转录本需要在插入新基因座之前被释放出来。我们利用基于结构的生物信息学方法，展示了跨越节肢动物、线虫和脊索动物门的几个逆转录转座子类群利用肝炎 Delta 病毒（HDV）家族的自我切割核酶来处理它们的 5' 末端。核酶终止的逆转录转座子包括 rDNA 特异性的 R2、R4 和 R6、端粒特异性的 SART、Baggins 和 RTE。R2 核酶的自我切割受到 rDNA 插入序列的强烈调节，最常见的插入序列促进更快的加工。核酶还在体外和体内促进下游开放阅读框的翻译起始。在一些生物体中，HDV 样核酶和锤头核酶似乎分别专门用于加工长散布元件和短散布元件。HDV 样核酶在非 LTR 逆转录转座中具有多种不同的功能，包括 5' 加工、翻译起始和潜在的转模板。
