- 著者
- Tahara Makoto Yamashita Hiroki
- 出版者
- 岡山大学農学部
- 雑誌
- 岡山大学農学部学術報告 (ISSN:04740254)
- 巻号頁・発行日
- vol.96, no.1, pp.7-11, 2007-02
Sequence analysis of Rtsp-1, an active LTR retrotransposon in the sweetpotato genome,revealed a possible novel Rtsp-1 RNA/tRNAMet complex for initiation of reverse transcription and the first DNA strand transfer. The Rtsp-1 RNA has a primer binding site (PBS) that is partly complementary to the 3' end of tRNAMet, and possesses an additional sequence complementary to the 5' end of tRNAMet downstream of the PBS. These additional base-pairings might stabilize the Rtsp-1 RNA/primer complex. In the free form, the 5' LTR of Rtsp-1 appears to form a stemloop structure apparently preventing the initiation of reverse transcription. While the stemforming site adjacent to the PBS is complementary to the tRNAMet, the other stem-forming site on the LTR complements a region just upstream of the 3' LTR. Additionally, another region at the 3' end of the Rtsp-1 RNA shows sequence complementarity to the tRNAMet. As the 3' end of Rtsp-1 approaches the tRNAMet bound to the PBS, the stem-forming strands dissociate and basepair with their complementary regions in the tRNAMet and the 3' end of Rtsp-1, respectively. Consequently, the LTR loop opens, allowing reverse transcription to initiate. After the initialreverse transcription stops at the 5' end of the Rtsp-1 RNA, the synthesized minus strand DNA needs to be transferred to the 3' end of the RNA to synthesize internal sequences. The Rtsp-1 RNA/tRNAMet complex may have evolved to facilitate this DNA transfer. Similar RNA/tRNA initiation complexes have been reported from reverse transcription in retroviruses and yeast retrotransposons (Ty1 and Ty3).カルスにおける転移が示されたサツマイモ LTR 型レトロトランスポゾン(Rtsp-1)の塩基配列を調べたところ,逆転写が開始される際,転写された Rtsp-1の RNA と最初の逆転写のプライマーに使われる tRNAMETとの間で,特徴的な逆転写開始複合体を形成し,この複合体が最初の逆転写とその後の過程で必要な逆転写産物(cDNA)の転移などを確実なものとしていることが示唆された.その内容は,1)転写された Rtsp-1の RNA 逆転写開始部位の塩基配列は自身の LTR 配列とステム構造をとること,2)tRNAMETが結合する Rtsp-1の Primer Binding Site 部位には,プライマーの機能を果たす tRNAMETの3'末端の相補配列に加えて,その隣接部位に tRNAMETの5'末端部位と相補的な結合部位が存在するために,tRNAMETの両末端が結合すること,3)Rtsp-1の3'末端側に,tRNAMET及びステム構造に関わる5'LTR の部位との相補配列があり,この3セ末端側が転写開始複合体と結合することにより,ステム構造が崩れて逆転写が開始されると推定されること,4)逆転写が開始された後も,tRNAMETの結合によってRtsp-1の5'末端と3'末端側に近接した状態が保たれることである.Rtsp-1の3セ末端側の転写開始複合体への結合を転写開始の条件とすることにより,最初に合成される cDNA の3'末端への転移が容易となることなどが示唆された.
- 著者
- Yamashita Hiroki Kasahara Jiro Sugiyama Yuta Matsuo Akiko
- 出版者
- Elsevier Inc.
- 雑誌
- Combustion and flame (ISSN:00102180)
- 巻号頁・発行日
- vol.159, no.9, pp.2954-2966, 2012-09
- 被引用文献数
- 47 1
This study was a numerical and experimental investigation of low-temperature auto-ignitions behindreflected shock waves in which a shock tube was employed as the experimental system. We used ahigh-speed video camera and the Schlieren method to visualize the ignition phenomena. Experimentswere performed over a temperature range from 549 ± 10 to 1349 ± 11 K and a pressure range from56 ± 2 to 203 ± 13 kPa, and a non-diluted stoichiometric acetylene–oxygen mixture was chosen as thecombustible gas. We introduced a numerical simulation to help us understand the disturbed temperaturedistribution behind bifurcated shock waves due to interference between reflected shock waves and theboundary layer developed behind incident shock waves. Additionally, we experimentally observed andevaluated quantitatively a tendency for ignition positions to be located farther from the reflecting wallas the temperature decreased behind reflected shock waves. To focus our attention on the ignition positions,we classified the ignition types behind reflected shock waves as near-wall ignition and far-wallignition by 4.7 mm distance from reflecting wall. The criterion for these ignition types was estimatedto be -1.0≦(∂ti/∂T5t)p5t≦-0.5. As a main object in this manuscript, we proposed an ignition modelin which local ignition is induced at some distance from reflecting wall based on the numerical simulationand results; the local ignitions at a point distant from the reflecting wall are induced by the temperaturerise, with the distance from the reflecting wall, immediately behind concave reflected shock wavesdue to developing of bifurcated shock waves. We confirmed that there is no discrepancy between the proposedmodel and experimental results.