新外显子的起源与功能及短同源序列介导转录滑动产生嵌合RNA 的研究

新外显子的起源是一种重要的增加转录组和蛋白质组多样性的分子机制。 对于新外显子及其父本基因的进化和功能特征方面还有很多重要的问题有待于 解决。本研究首先在全基因组水平上鉴定在人和小鼠中产生的新外显子，随后 对这些外显子及其父本基因作进化和功能上的分析。我们发现新外显子倾向于 位于基因的UTR 区域，尤其是5’ UTR 区域，这表明可能有些新外显子的出现 与基因的表达调控相关。我们还发现，产生新外显子的基因具有较高的组织表 达特异性，其基因功能倾向于细胞调控和与外界环境相互作用。通过对外群中 直系同源基因的分析，我们的结果表明进化速率较高的基因更容易获得新的外 显子，纠正了先前认为的获得新外显子会加速基因进化速率的看法。 我们对哺乳类CDYL 基因家族中产生的新外显子进行了具体的进化分析和 功能研究。我们的结果表明CDYL 基因在哺乳类分化前在原先的基因上游区域 获得了一个新的启动子和三个新的外显子。随后在哺乳动物各个支系的分化中， CDYL 基因在小鼠，狗和人中分别独立的进化出一个新的外显子。同源比对的 结果表明，这些新外显子是通过内含子序列的外显子化这一分子机制产生。近 缘物种间的进化速率的计算结果表明这些新产生的外显子具有快速进化的模 式，并且其快速进化可能是由正选择所驱动。在人中，多种突变包括新外显子 的获得，启动子的改变，选择性剪切的发生使得人的CDYL 基因获得了一种新 的编码更长蛋白质的剪切体。在人Hela 细胞系中的实验表明，新产生的蛋白质 与原有的蛋白质相比都具有显著的转录抑制活性，但新的蛋白质的转录抑制活 性较弱，且两者之间存在相互干扰的关系。这一结果表明通过新外显子的获得 产生的新的蛋白质可以丰富原有的基因表达调控体系，使得生物体的调控网络 更加精确。 嵌合RNA 通常认为是由来源于不同的pre-mRNA 的外显子通过反式剪切连 接在一起形成的。这一现象在包括多种动物和植物中被广泛的报道。我们的研 究首先通过大规模表达序列（ESTs）的搜索，在酵母，果蝇，小鼠和人中鉴定 到了大量的嵌合RNA。这一结果表明形成嵌合RNA 在真核生物中是一种普遍 的生物学过程，是一种重要的增加转录组和蛋白质组的多样性的分子机制。对 嵌合RNA 的序列分析表明，仅有<20%的嵌合RNA 在接合处可以找到典型的剪切位点 GU-AG，可以用经典的反式剪切模型来解释其产生机制。然而有意思的 是，我们在大约一半的嵌合RNA 的供体基因之间找到了短的同源序列，这一发 现使我们提出了一种新的分子机制来解释这些嵌合RNA 的形成，我们称之为 “转录滑动”模型。在酵母我们，我们用实验的方法验证了短同源序列对形成嵌 合RNA 的必要性，有力地支持了我们这一模型。

干扰RNA(RNAi)作用机理及其在植物细胞工程中的应用进展

随着RNAi调控目的基因表达机理研究的深入,RNAi技术也发展为一种强有力的实验工具,用来控制目的基因的表达以获取预期的生物表型。目前在植物中至少发现存在三种不同的RNAi途径,这些途径中基因沉默信号可以放大、传递和自我调控。为了建立高效、经济的RNAi技术体系,必须解决以下几个问题:即RNAi的有效传递,稳定性的提高,非目标效应出现的减小以及目标RNA敏感位点的确定等。综述了RNAi作用机制及其在植物细胞工程中的最新应用进展,并详细探讨了其技术体系。

果树组织中总RNA提取的新方法

本研究设计了一种新的RNA提取方法 ,解决了RNA提取时容易被降解和污染这一关键问题。通过加入Rnase抑制剂 ,消除了同外源RNase对RNA的降解 ,结合DNA难呈低盐溶液(140mmol·L -1NaCl)的原理 ,去除了DNA对RNA提取液的污染 ;先后使用酚和氯仿 ,有效地去除了蛋白质和酚类物的污染 ,利用抗氧化剂PVP和巯基乙醇 ,消除了内源酚类物质氧化变色对病毒RNA逆转录的影响。采用上述方法可以在4～5h内得到纯度高、含量大、完整性好的果树总RNA ,并获得了逆转录活性较强的病毒RNA ,同时使提取RNA的成本降低。这些方法对苹果、葡萄、桃、樱桃等果树总RNA的提取均适用。

土壤中Frankia菌RNA提取

土壤中Ｆｒａｎｋｉａ菌ＲＮＡ提取王育英，林建群，郭秀荣，李彤，张忠泽（中国科学院沈阳应用生态研究所，１１００１５）Ｆｒａｎｋｉａ非亚科共生固氮是一类重要的固氮资源。对Ｆｒａｎｋｉａ共生生物学、生态学等特性曾进行过广泛的研究。８ｔ０年代末，Ｆｒａｎｋｉ...

Self-assembly of single-stranded RNA on carbon nanotube: Polyadenylic acid to form a duplex structure

All messenger-RNA (mRNA) molecules in eukaryotic cells have a polyadenylic acid [poly (rA)] tail at the 3'-end and human poly (rA) polymerase (PAP) has been considered as a tumor-specific target. A ligand that is capable of recognizing and binding to the poly(M) tail of mRNA might interfere with the full processing of mRNA by PAP and can be a potential therapeutic agent. We report here for the first time that single-walled carbon nanotubes (SWNTs) can cause single-stranded poly (M) to self-structure and form a duplex structure, which is studied by UV melting, atomic force microscopy, circular dichroism spectroscopy, and NMR spectrometry.

Targeted RNA interference of cyclin A(2) mediated by functionalized single-walled carbon nanotubes induces proliferation arrest and apoptosis in chronic myelogenous leukemia K562 cells

Cyclin A(2) plays critical role in DNA replication, transcription, and cell cycle regulation. Its overexpression has been detected and related to many types of cancers including leukemia, suggesting that suppression of cyclin A(2) would be an attractive strategy to prevent tumor progression. Herein, we apply functionalized single wall carbon nanotubes (f-SWNTs) to carry small interfering RNA (siRNA) into K562 cells and determine whether inhibition of cyclin A(2) would be a potential therapeutic target for chronic myelogenous leukemia.

Changes in RNA, DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles

The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid-based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post-metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage-specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post-metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre-metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre-metamorphic larval phase. Growth was dominantly hypertrophical from the early- to mid-metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.

The immune responses in Chinese mitten crab Eriocheir sinensis challenged with double-stranded RNA

Double-stranded RNA (dsRNA) is a virus-associated molecular pattern which induces antiviral innate immune responses and RNA interference (RNAi) in mammals. In invertebrates, RNAi phenomenon has been widely studied, but dsRNA-induced innate immune response is seldom reported. In the present study, two different dsRNAs specific for green fluorescent protein (GFP) and the putative D1 protein of photosystem II (NoPSD) from Nannochloropsis oculata, were employed to challenge Chinese mitten crab Eriocheir sinensis. The temporal changes of phenoloxidase (PO), acid phosphatase (ACP), superoxide dismutase (SOD) and malondialdehyde (MDA) content, as well as the mRNA expression of some immune-related genes were examined in order to estimate the effect of dsRNAs on the innate immunity of E. sinensis. The activities of PO, ACP and SOD significantly increased after dsRNA treatment, whereas malondialdehyde (MDA) content did not change significantly. Among the examined genes, only the mRNA expression of EsALF, an antibacterial peptide in E. sinensis, was significantly up-regulated (about 5 fold, P < 0.05) at 12 h after dsRNA treatment, while no significant expression changes were observed among the other immune genes. The increase of PO, ACP and SOD activities, and mRNA expression level of EsALF after dsRNA stimulation indicate that phenoloxidase, hydrolytic enzyme, antioxidation and EsALF were involved in dsRNA-induced innate immunity, suggesting that broad-spectrum immune responses could be induced by dsRNA in E. sinensis. (C) 2009 Elsevier Ltd. All rights reserved.

Molecular characterization and effect of RNA interference of retinoid X receptor (RXR) on E75 and chitinase gene expression in Chinese shrimp Fenneropenaeus chinensis

Retinoid X receptor (RXR)/ultraspiracle (USP) is the heterodimeric partner of ecdysteroid receptor and is required for the molting process of arthropods. To better understand the molecular aspects governing the process of molting in shrimp, the full-length cDNA of two RXRs, named as FcRXR-1 and FcRXR-2 were obtained from Chinese shrimp Fenneropenaeus chinensis which were of 1715 and 1700 bp long, revealed a 1315 and 1300 bp open reading frame (ORF) respectively. Quantitative Real time PCR analysis showed a marked tissue-specific difference in the expression of FcRXR transcript, which revealed that the expression of FcRXR Could be regulated in a tissue-specific manner. Moreover, high expression of FcRXR mRNAs was observed in late pre-molt period (D3) and post molt stages (A-B) of shrimp. Among the two isoforms, FcRXR-2 appeared in a considerably high level in all the stages compared to the FcRXR-1. In addition, we examined the temporal expression of two chitinase genes: FcChitinase (FcChi) and FcChitinase-1 (FcChi-1) during the molt cycle of F chinensis. Both the FcChi and FcChi-1 transcripts were detected in all stages of molting, although considerable fluctuations observed through the molt cycle. Injection of double stranded RXR (dsRXR) into juvenile shrimp resulted in a maximum silencing effect at 48 h post injection. We analyzed the expression levels of FcChi, FcChi-1 and the ecdysone inducible gene E75 (FcE75) in samples of dsRXR injected shrimp. Significant reduction in levels of both FcE75, FcChi and FcChi-1 transcripts Occurred in the silenced shrimp. This correlation suggested that RXR might involve in the downstream regulation of E75 and chitinase gene transcription in the ecdysone signaling pathway of decapod crustaceans. (C) 2009 Published by Elsevier Inc.

Improved RNA isolation from Laminaria japonica Aresch (Laminariaceae, Phaeophyta)

RNA isolation is difficult in some plants and algae because phenolics, polysaccharides, or other compounds can bind or co-precipitate with RNA, and because the success of RNA isolation can be strain-specific and species-specific. To create an improved RNA isolation protocol for Laminaria japonica Aresch (Laminariaceae, Phaeophyta), four methods for extracting RNA were tested. A cetyltrimethylammonium bromide (CTAB)-based RNA extraction protocol was developed that clearly showed 28S and 18S ribosomal RNA bands and produced RNA with high yield (68 mu g g(-1) fresh weight) and high quality (A (260/280) ratio 1.96 +/- 0.05). The isolated RNA was intact, and RT-PCR analysis confirmed that further molecular application is feasible.

Identification of peptides that bind with thymidylate synthase RNA using mRNA display technique

Using in vitro selection method to isolate nucleic acids, peptides and proteins has been studied intensively in recent years. In vitro mRNA display is a new and effective technique for peptides selection, and the rationale of this technique is that a synthetic mRNA with puromycin could covalently link with the protein that it encodes, thus an mRNA-protein fusion is formed. This approach has been used in identification of many functional peptides. The peptides binding with thymidylate synthase RNA were isolated using mRNA display technique from a large peptide library (>10(13) different sequences). The selection scheme was constructed, and the experimental conditions, including library synthesis, formation of RNA-peptide fusion and RNA immobilization were optimized. Eight cycles have been processed and the results confirmed that the selected peptides could bind with thymidylate synthase mRNA specifically. Compared the amino acid sequences of the selected peptides with those from the initial random library, the basic and aromatic residues in selected peptides were enriched significantly, suggesting these peptide regions may be important in the peptide-TS mRNA interaction. As a novel in vitro selection approach, mRNA display technique would be developed as a powerful tool for isolation of functional peptides and proteins that could interact with immobilized targets with high affinity and specificity.

A key gene of the RNA interference pathway in the black tiger shrimp, Penaeus monodon: Identification and functional characterisation of Dicer-1

RNA interference (RNAi) is an evolutionarily conserved mechanism by which double-stranded RNA (dsRNA) initiates post-transcriptional silencing of homologous genes. Here we report the amplification and characterisation of a full length cDNA from black tiger shrimp (Penaeus monodon) that encodes the bidentate RNAase III Dicer, a key component of the RNAi pathway. The full length of the shrimp Dicer (Pm Dcr1) cDNA is 7629 bp in length, including a 51 untranslated region (UTR) of 130 bp, a 3' UTR of 77 bp, and an open reading frame of 7422 bp encoding a polypeptide of 2473 amino acids with an estimated molecular mass of 277.895 kDa and a predicted isoelectric point of 4.86. Analysis of the deduced amino acid sequence indicated that the mature peptide contains all the seven recognised functional domains and is most similar to the mosquito (Aedes aegypti) Dicer-1 sequence with a similarity of 34.6%. Quantitative RT-PCR analysis showed that Pm Dcr1 mRNA is most highly expressed in haemolymph and lymphoid organ tissues (P 0.05). However, there was no correlation between Pm Dcr1 mRNA levels in lymphoid organ and the viral genetic loads in shrimp naturally infected with gill-associated virus (GAV) and Mourilyan virus (P > 0.05). Treatment with synthetic dsRNA corresponding to Pm Dcr1 sequence resulted in knock-down of Pm Dcr1 mRNA expression in both uninfected shrimp and shrimp infected experimentally with GAV. Knock-down of Pm Dcr1 expression resulted in more rapid mortalities and higher viral loads. These data demonstrated that Dicer is involved in antiviral defence in shrimp. (c) 2007 Elsevier Ltd. All rights reserved.

Species identification in salted products of red snappers by semi-nested PCR-RFLP based on the mitochondria 12S rRNA gene sequence

A molecular approach was developed to distinguish species of red snappers among commercial salted fish products. The specific fragments of the mitocliondrial 12S rRNA gene, which were about 450 bp, were obtained using the semi-nested polymerase chain reaction (semi-nested PCR). Subsequently, PCR amplicons were sequenced, aiming to select restriction endonucleases that generated species-specific restriction fragment length polymorphism (RFLP) profiles. Discrimination of red snappers Lutjanus sanguineus, L. erythopterus from L. argentintaculatus, L. malabarius and other morphologically similar fishes such as Lethrinus leutjanus and Pinjalo pinjalo was feasible by one restriction digestion reaction with three endonucleases Hae III, Sca I and SnaB I, however, for differentiation of L. sattguineus and L. erythopterus, another restriction digestion reaction with single restriction endonuclease Mae II was needed. The seminested PCR-RFLP was demonstrated to be reliable in species identification of salted fish products in this study. (c) 2005 Published by Elsevier Ltd.