Volume 30 Issue 3 - March 4, 2016 PDF
Mechanism by which a LINE protein recognizes its 3′ tail RNA.
Y. Hayashi1, M. Kajikawa1, T. Matsumoto1, & N. Okada1,2,3,*
1 Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B-21 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan
2 Department of Life Sciences, National Cheng Kung University, Tainan 701, Taiwan
3 Foundation for Advancement of International Science, Tsukuba 305-0821, Japan
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In 1996, our group for the first time showed that SINEs and LINEs share the same tail sequence at the 3’ end which forms a stem-loop structure. This provided the possibility that in the case of SINE amplification the SINE borrows the amplification machinery of LINEs. LINE encodes RT (reverse-transcriptase) and generally the RT recognizes the LINE tail for amplification to initiate reverse transcription. This hypothesis was experimentally verified also by our group in 2002 (Kajikawa & Okada, Cell). In this article we used two different types of LINEs, which are phylogenetically closely related but have different tail sequences to analyze the recognition mechanism of their tail sequences. We demonstrated that the region between the endonuclease and RT domains in ORF2 is the site at which the proteins bind the stem-loop structure of the 3’ tail RNA, showing the strict recognition of the stem-loop structure by the cognate ORF2 protein is an important step in retrotransposition. This recognition can be bipartite, involving the general recognition of the stem by cTBR (conserved tail-binding region) of ORF2 and the specific recognition of the loop by vTBR (variable tail-binding region). This is the first report that clearly characterized the RNA-binding region in ORF2, providing the generality for the recognition mechanism of the RNA tail by the ORF2 protein encoded by LINEs.
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