Both catalytic steps of nuclear pre-mRNA splicing are reversible

Nuclear pre-messenger RNA (pre-mRNA) splicing is an essential processing step for the production of mature mRNAs from most eukaryotic genes. Splicing is catalyzed by a large ribonucleoprotein complex, the spliceosome, which is composed of five small nuclear RNAs and more than 100 protein factors. Despite the complexity of the spliceosome, the chemistry of the splicing reaction is simple, consisting of two consecutive transesterification reactions. The presence of introns in spliceosomal RNAs of certain fungi has suggested that splicing may be reversible; however, this has never been demonstrated experimentally. By using affinity-purified spliceosomes, we have shown that both catalytic steps of splicing can be efficiently reversed under appropriate conditions. These results provide considerable insight into the catalytic flexibility of the spliceosome.     

Structure of the exon junction core complex with a trapped DEAD-box ATPase bound to RNA

In higher eukaryotes, a multiprotein exon junction complex is deposited on spliced messenger RNAs. The complex is organized around a stable core, which serves as a binding platform for numerous factors that influence messenger RNA function. Here, we present the crystal structure of a tetrameric exon junction core complex containing the DEAD-box adenosine triphosphatase (ATPase) eukaryotic initiation factor 4AIII (eIF4AIII) bound to an ATP analog, MAGOH, Y14, a fragment of MLN51, and a polyuracil mRNA mimic. eIF4AIII interacts with the phosphate-ribose backbone of six consecutive nucleotides and prevents part of the bound RNA from being double stranded. The MAGOH and Y14 subunits lock eIF4AIII in a prehydrolysis state, and activation of the ATPase probably requires only modest conformational changes in eIF4AIII motif I.     

肌肉生长发育可变剪接研究进展

为了解动物肌肉生长发育可变剪接调控过程最新研究,本文对近年来人、小鼠和其他多种动物肌肉生长发育的可变剪接调控的相关研究进行了整理与分析,总结了肌肉生长发育可变剪接的发生、调控蛋白多样性的分子机制、人和动物的肌肉发育过程中可变剪接的调控研究进展及可变剪接的数据量化方法.结果 表明:肌肉是表现出最高水平的组织特异性和保守可...     

The snoRNA HBII-52 regulates alternative splicing of the serotonin receptor 2C

The Prader-Willi syndrome is a congenital disease that is caused by the loss of paternal gene expression from a maternally imprinted region on chromosome 15. This region contains a small nucleolar RNA (snoRNA), HBII-52, that exhibits sequence complementarity to the alternatively spliced exon Vb of the serotonin receptor 5-HT(2C)R. We found that HBII-52 regulates alternative splicing of 5-HT(2C)R by binding to a silencing element in exon Vb. Prader-Willi syndrome patients do not express HBII-52. They have different 5-HT(2C)R messenger RNA (mRNA) isoforms than healthy individuals. Our results show that a snoRNA regulates the processing of an mRNA expressed from a gene located on a different chromosome, and the results indicate that a defect in pre-mRNA processing contributes to the Prader-Willi syndrome.     

草鱼CC趋化因子基因CCL24及其可变剪接

CC趋化因子是一类能够促进动物体内炎症部位的各种白细胞的补充、激活和黏附的趋化性细胞因子家族,是鱼类天然免疫系统的重要组成部分。分析了从草鱼肠道cDNA文库中筛选到的CC趋化因子基因CCL24,并克隆了阅读框区域内的基因组序列。序列分析表明,CCL24基因由4个外显子和3个内含子组成;外显子拼接的序列与CCL24cDNA序列完全一致,编码95个氨基酸,有2个相邻的半胱氨酸(CC),为典型的CC趋化因子亚家族成员。此外,还发现草鱼CCL24基因存在可变剪接现象,第1内含子没有被剪切掉的非正常转录本翻译后可能产生没有CC趋化因子活性的24个氨基酸的短肽,而且这种转录本在精巢、头肾、皮肤、肝胰脏、肠道、肌肉、肾脏等组织均检测到;而正常剪接的CCL24转录本,仅在肾脏和肠道中检测到,且其表达量要明显低于非正常剪接的转录本。     

草鱼CC趋化因子基因CCL24及其可变剪接

CC趋化因子是一类能够促进动物体内炎症部位的各种白细胞的补充、激活和黏附的趋化性细胞因子家族,是鱼类天然免疫系统的重要组成部分。分析了从草鱼肠道cDNA文库中筛选到的CC趋化因子基因CCL24,并克隆了阅读框区域内的基因组序列。序列分析表明,CCL24基因由4个外显子和3个内含子组成;外显子拼接的序列与CCL24cDNA序列完全一致,编码95个氨基酸,有2个相邻的半胱氨酸(CC),为典型的CC趋化因子亚家族成员。此外,还发现草鱼CCL24基因存在可变剪接现象,第1内含子没有被剪切掉的非正常转录本翻译后可能产生没有CC趋化因子活性的24个氨基酸的短肽,而且这种转录本在精巢、头肾、皮肤、肝胰脏、肠道、肌肉、肾脏等组织均检测到;而正常剪接的CCL24转录本,仅在肾脏和肠道中检测到,且其表达量要明显低于非正常剪接的转录本。     

草鱼MKLN1基因可变剪接和微卫星序列的多态性

MKLN1基因编码的muskelin蛋白主要通过其羧基端的kelch重复结构域与其它蛋白形成复合物行使功能。通过分析草鱼鳃组织的基因转录谱,发现其中的MKLN1基因存在(CT)15的微卫星序列,通过检测3个不同的草鱼种群,又发现(CT)9、(CT)10、(CT)11和(CT)13 4种多态性序列。通过克隆该段MKLN1基因组序列并与斑马鱼和红鳍东方鲀的MKLN1基因组序列比较,发现克隆得到的草鱼基因序列是由一个内含子和两个外显子组成,共编码144个氨基酸。通过进一步调查不同组织该基因的转录本,发现存在内含子剪接和内含子未被剪接的两个转录本。由于内含子序列未被剪接的转录本在内含子中存在TGA终止密码子,导致MKLN1基因翻译提前终止,翻译产物为失去部分kelch结构域的muskelin蛋白。相对于内含子正常剪接的转录本,没有被剪接内含子的转录本在各种组织中的表达量要明显低得多。简而言之,本研究发现了草鱼MKLN1转录本中的微卫星序列是来自未被剪切的内含子,而未被剪切的内含子导致该转录本编码部分kelch结构域缺失的muskelin蛋白。研究亮点:目前对于可直接锚定功能基因的I型微卫星标记研究很少。本文首次发现M...     

春性甘蓝型油菜FCA同源基因可变剪接体的克隆及表达研究

【目的】克隆特早熟春性甘蓝型油菜的FCA同源基因(sBnFCA)及其可变剪接体,并分析该基因的表达模式。【方法】根据拟南芥和芸薹属植物FCA基因的DNA序列和cDNA序列设计引物,用PCR和RT-PCR技术克隆特早熟春性甘蓝型油菜"86号"的FCA同源基因(sBnFCA)及其可变剪接体,对克隆基因及编码蛋白序列进行生物信息学分析,构建系统进化树,并用qRT-PCR技术检测sBnFCA基因在不同发育时期根、茎、叶、茎尖中的表达量。【结果】克隆出了sBnFCA基因的全长序列(8 827bp),得到了sBnFCA-γ可变剪接体及一个新的可变剪接体(sBnFCA-5),新的可变剪接体在GenBank中的登录号为KJ701579.1。sBnFCA-5剪接体的CDS全长1 986bp,编码662个氨基酸残基,其推导的氨基酸序列具有2个保守的RRM结构域和1个WW结构域。生物信息学分析显示,sBnFCA-5与已报道甘蓝型油菜BnFCA-γ(AF414188.1)的相似性达99%,与拟南芥FCA-γ的相似性达87%。sBnFCA-5比sBnFCA-γ少了172个碱基序列,是一个跨外显子剪接体。sBnFCA蛋白相对分子质量和理论等电点分别为72.5ku和9.2。基因表达模式分析显示,sBnFCA-γ和sBnFCA-5在苗期、蕾期、花期的根、茎、叶和茎尖组织中都有表达,sBnFCA-γ在蕾期茎尖和花期叶片中表达量较高,sBnFCA-5在蕾期茎尖和花期叶片中表达量极高。【结论】克隆的sBnFCA-5为甘蓝型油菜sBnFCA基因的一个新的可变剪接体,该基因在春性特早熟甘蓝型油菜开花调控中可能有着重要的调节作用。     

基于全长转录组测序的牛脂肪组织可变剪接事件分析

为探究可变剪接影响下更为复杂的脂肪沉积调控网络,明晰可变剪接事件的发生对脂肪沉积调控机制的影响,本研究基于PacBio测序平台的第三代测序技术,对夷陵黄牛腹腔脂肪、皮下脂肪、肌间脂肪进行全长转录组测序分析。共发现15 445个基因检测到50 520个可变剪接,占牛全部基因的33.4%。对这些基因进行富集分析发现,83个GO条目显著富集,这些显著富集的通路可能参与脂肪沉积网络的调控,其中16个与脂质合成及代谢相关,27条KEGG通路显著富集,其中15条与脂质合成及代谢相关。使用KOG、KEGG、NR、Swiss Prot、GO数据库对测序序列进行注释,80 756条序列共注释到69 259个基因,94 458条CDS序列及对应的pep序列。其中GO分析中15 039条序列富集到507个生物学过程条目,7 907条序列富集到214个细胞组分条目,30 672条序列富集到559个分子功能条目。KEGG数据分析富集到34条通路共49 710条序列,其中7 002条序列参与信号转导途径。以上结果表明,牛脂肪组织存在大量可变剪接事件,并且这些发生可变剪接事件的基因对脂肪沉积的调控发挥重要作用,这可...     

豚鼠ESR2基因新的可变剪接体克隆及序列分析

[目的]对豚鼠雌激素受体2(ESR2)基因进行克隆及序列分析,并预测分析其编码的蛋白序列,为提高豚鼠产仔性能及其育种打下基础.[方法]根据GenBank已公布的豚鼠ESR2基因序列(登录号XM003472337)设计引物,以豚鼠卵巢组织总RNA为模板,RT-PCR扩增ESR2基因编码区序列(CDS),利用生物信息学分析其编码蛋白氨基酸的组成及理化性质、二级结构及与相关物种的同源性.[结果]克隆获得的豚鼠ESR2基因CDS长度为1650bp,编码549个氨基酸,比参照序列(XM 003472337)少54个碱基,是ESR基因新的可变剪接体,且第7外显子缺失;蛋白质二级结构预测结果表明,豚鼠ESR2成熟肽包含α螺旋、β折叠和无规卷曲3种二级结构元件,由于缺失18个氨基酸导致蛋白质结构发生变异;同源性分析结果显示,豚鼠与长尾龙猫、奥氏更格卢鼠、马、达马拉鼹鼠、裸鼢鼠、鼠狐猴、八齿鼠、猪和人的ESR2基因序列同源性分别为91%、87%、86%、91%、92%、86%、88%、92%和86%.[结论]克隆获得的豚鼠ESR2基因为新的可变剪接体,可作为研究豚鼠产仔性能及豚鼠育种重要的候选基因之一.     

Predictive identification of exonic splicing enhancers in human genes

Specific short oligonucleotide sequences that enhance pre-mRNA splicing when present in exons, termed exonic splicing enhancers (ESEs), play important roles in constitutive and alternative splicing. A computational method, RESCUE-ESE, was developed that predicts which sequences have ESE activity by statistical analysis of exon-intron and splice site composition. When large data sets of human gene sequences were used, this method identified 10 predicted ESE motifs. Representatives of all 10 motifs were found to display enhancer activity in vivo, whereas point mutants of these sequences exhibited sharply reduced activity. The motifs identified enable prediction of the splicing phenotypes of exonic mutations in human genes.     

基于RNA-seq数据分析玉米抗虫响应基因的可变剪接事件

采用Illumina Hiseq~(TM)分别对黏虫取食的玉米叶片及对照组材料进行转录组测序,鉴定和分析响应黏虫取食基因的可变剪接事件。结果表明,对照组中鉴定出15 701个基因对应79 363个可变剪接事件,黏虫取食组中鉴定到11 791个基因的39 385个可变剪接事件。2组玉米基因组在不同的可变剪接类型中,均是以第1个外显子可变剪切、最后1个外显子可变剪切、单内含子滞留和可变5′或3′端剪切4种类型为主。对2组发生可变剪接事件的基因进行比对发现,黏虫处理组新增加了1 121个可变剪接基因,差异表达分析鉴定出177个表达显著差异的可变剪接基因。GO功能富集分析表明,发生可变剪接的差异基因主要富集于氧化还原酶活性、转移酶活性、DNA结合、ATP结合、代谢过程、以DNA为模板的转录及调控相关的功能,表明这些可变剪接差异表达基因参与了玉米的抗虫响应过程。     

Control of alternative splicing by the differential binding of U1 small nuclear ribonucleoprotein particle.

Cellular factors controlling alternative splicing of precursor messenger RNA are largely unknown, even though this process plays a central role in specifying the diversity of proteins in the eukaryotic cell. For the identification of such factors, a segment of the rat preprotachykinin gene was used in which differential expression of neuropeptides gamma and K is dependent on alternative splicing of the fourth exon (E4). Sequence variants of the three-exon segment, (E3-E4-E5) were created, resulting in a sensitive assay for factors mediating the splicing switch between E4-skipping and E4-inclusion. A dinucleotide mutation in the 5' splice site of E4 that increase base-pairing of this site to U1 small nuclear RNA resulted in uniform selection of E4, whereas a control mutation that destroyed base-pairing resulted in uniform E4-skipping. Affinity selection of spliceosomes formed on these functionally distinct substrates revealed that the extreme difference in splicing was mediated by differential binding of the U1 small nuclear ribonucleoprotein particle (snRNP) to the 5' splice site of E4. These data show that, apart from its established role in selecting 5' splice sites, U1 snRNP plays a fundamental role in 3' exon selection and provides insight into possible mechanisms of alternative splicing.     

马身猪ZNF280D基因新型剪接体的鉴定及生物信息学分析

[目的]本试验旨在探究马身猪中锌指蛋白(zinc finger protein)ZNF280D基因的剪接体类型。[方法]在猪转录组测序对ZNF280D基因剪切位置预测的基础上,采用RT-PCR和克隆测序技术对预测的剪切位点进行验证,检测该基因不同剪接体的结构并进行生物信息学分析。[结果]共检测到2个剪接体,分别是ZNF280D1和ZNF280D2,ZNF280D1为该基因的常规转录本,ZNF280D2第8外显子5'端大部分缺失。ZNF280D1含有3个C2H2型锌指结构域,属tC2H2型锌指蛋白,ZNF280 D2含有4个C2H2型锌指结构域,属maC2H2型锌指蛋白。[结论]ZNF280D2与DNA的亲和力大于ZNF280D1。