Alternative polyadenylation events in epithelial cells sense endometritis progression in dairy cows

Endometritis(inflammation of the endometrial lining) is one of the most devastating reproductive diseases in dairy cattle, resulting in substantial production loss and causing more than $650 million in lost revenue annually in the USA.We hypothesize that alternative polyadenylation(APA) sites serve as decisive sensors for endometrium health and disease in dairy cows. Endometrial cells collected from 18 cows with purulent vaginal discharge scored 0 to 2 were used for APA profiling with our whole transcriptome termini site sequencing(WTTS-seq) method. Overall, pathogens trigger hosts to use more differentially expressed APA(DE-APA), more intronic DE-APA, more DE-APA sites per gene and more DE-genes associated with inflammation. Host CD59 molecule(CD59), Fc fragment of IgG receptor IIa(FCGR2A), lymphocyte antigen 75(LY75) and plasminogen(PLG) may serve as initial contacts or combats with pathogens on cell surface, followed by activation of nuclear receptor subfamily 1 group H member 4(NR1H4) to regulate AXL receptor tyrosine kinase(AXL), FGR proto-oncogene, Src family tyrosine kinase(FGR), HCK protooncogene, Src family tyrosine kinase(HCK) and integrin subunit beta 2(ITGB2) for anti-inflammation. This study is the first to show significance of cilium pathways in endometrium health and animal reproduction. MIR21 and MIR30A would be perfect antagonistic biomarkers for diagnosis of either inflammation or anti-inflammation. These novel findings will set precedent for future genomic studies to aid the dairy industry develop new strategies to reduce endometritis incidence and improve fertility.

Alternative polyadenylation-related genetic variants contribute to bladder cancer risk

Aberrant alternative polyadenylation(APA)events play an important role in cancers,but little is known about whether APA-related genetic variants contribute to the susceptibility to bladder cancer.Previous genome-wide association study performed APA quantitative trait loci(apaQTL)analyses in bladder cancer,and identified 17955 single nucleotide polymorphisms(SNPs).We found that gene symbols of APA affected by apaQTL-associated SNPs were closely correlated with cancer signaling pathways,high mutational burden,and immune infiltration.Association analysis showed that apaQTL-associated SNPs rs34402449 C>A,rs2683524 C>T,and rs11540872 C>G were significantly associated with susceptibility to bladder cancer(rs34402449:OR=1.355,95%confidence interval[CI]:1.159-1.583,P=1.33×10^(−4);rs2683524:OR=1.378,95%CI:1.164-1.632,P=2.03×10^(−4);rs11540872:OR=1.472,95%CI:1.193-1.815,P=3.06×10^(−4)).Cumulative effect analysis showed that the number of risk genotypes and smoking status were significantly associated with an increased risk of bladder cancer(P_(trend)=2.87×10^(−12)).We found that PRR13,being demonstrated the most significant effect on cell proliferation in bladder cancer cell lines,was more highly expressed in bladder cancer tissues than in adjacent normal tissues.Moreover,the rs2683524 T allele was correlated with shorter 3′untranslated regions of PRR13 and increased PRR13 expression levels.Collectively,our findings have provided informative apaQTL resources and insights into the regulatory mechanisms linking apaQTL-associated variants to bladder cancer risk.

Alternative polyadenylation:An untapped source for prostate cancer biomarkers and therapeutic targets?

Objective:To review alternative polyadenylation(APA)as a mechanism of gene regulation and consider potential roles for APA in prostate cancer(PCa)biology and treatment.Methods:An extensive review of mRNA polyadenylation,APA,and PCa literature was performed.This review article introduces APA and its association with human disease,outlines the mechanisms and components of APA,reviews APA in cancer biology,and considers whether APA may contribute to PCa progression and/or produce novel biomarkers and therapeutic targets for PCa.Results:Eukaryotic mRNA 30-end cleavage and polyadenylation play a critical role in gene expression.Most human genes encode more than one polyadenylation signal,and produce more than one transcript isoform,through APA.Polyadenylation can occur throughout the gene body to generate transcripts with differing 30-termini and coding sequence.Differences in 30-untranslated regions length can modify post-transcriptional gene regulation by microRNAs and RNA binding proteins,and alter mRNA stability,translation efficiency,and subcellular localization.Distinctive APA patterns are associated with human diseases,tissue origins,and changes in cellular proliferation rate and differentiation state.APA events may therefore generate unique mRNA biomarkers or therapeutic targets in certain cancer types or phenotypic states.Conclusions:The full extent of cancer-associated and tissue-specific APA events have yet to be defined,and the mechanisms and functional consequences of APA in cancer remain incompletely understood.There is evidence that APA is active in PCa,and that it may be an untapped resource for PCa biomarkers or therapeutic targets.

Disruption of PABPN1 phase separation by SNRPD2 drives colorectal cancer cell proliferation and migration through promoting alternative polyadenylation of CTNNBIP1

Generally shortened 3′UTR due to alternative polyadenylation(APA)is widely observed in cancer,but its regulation mechanisms for cancer are not well characterized.Here,with profiling of APA in colorectal cancer tissues and poly(A)signal editing,we firstly identified that the shortened 3′UTR of CTNNIBP1 in colorectal cancer promotes cell proliferation and migration.We found that liquid-liquid phase separation(LLPS)of PABPN1 is reduced albeit with higher expression in cancer,and the reduction of LLPS leads to the shortened 3′UTR of CTNNBIP1and promotes cell proliferation and migration.Notably,the splicing factor SNRPD2 upregulated in colorectal cancer,can interact with glutamic-proline(EP)domain of PABPN1,and then disrupt LLPS of PABPN1,which attenuates the repression effect of PABPN1 on the proximal poly(A)sites.Our results firstly reveal a new regulation mechanism of APA by disruption of LLPS of PABPN1,suggesting that regulation of APA by interfering LLPS of 3′end processing factor may have the potential as a new way for the treatment of cancer.

mRNA alternative polyadenylation (APA) in regulation of gene expression and diseases

The mRNA polyadenylation plays essential function in regulation of mRNA metabolism.Mis-regulations of mRNA polyadenylation are frequently linked with aberrant gene expression and disease progression.Under the action of polyadenylate polymerase,poly(A)tail is synthesized after the polyadenylation signal(PAS)sites on the mRNAs.Alternative polyadenylation(APA)often occurs in mRNAs with multiple poly(A)sites,producing different 3'ends for transcript variants,and therefore plays important functions in gene expression regulation.In this review,we first summarize the classical process of mRNA 3'-terminal formation and discuss the length control mechanisms of poly(A)innucleus and cytoplasm.Thenwe review the research progress on alternative polyadenylation regulation and the APA site selection mechanism.Finally,we summarize the functional roles of APA in the regulation of gene expression and diseases including cancers.

stAPAminer:Mining Spatial Patterns of Alternative Polyadenylation for Spatially Resolved Transcriptomic Studies

Alternative polyadenylation(APA)contributes to transcriptome complexity and gene expression regulation and has been implicated in various cellular processes and diseases.Singlecell RNA sequencing(scRNA-seq)has enabled the profiling of APA at the single-cell level;however,the spatial information of cells is not preserved in scRNA-seq.Alternatively,spatial transcriptomics(ST)technologies provide opportunities to decipher the spatial context of the transcriptomic landscape.Pioneering studies have revealed potential spatially variable genes and/or splice isoforms;however,the pattern of APA usage in spatial contexts remains unappreciated.In this study,we developed a toolkit called stAPAminer for mining spatial patterns of APA from spatially barcoded ST data.APA sites were identified and quantified from the ST data.In particular,an imputation model based on the k-nearest neighbors algorithm was designed to recover APA signals,and then APA genes with spatial patterns of APA usage variation were identified.By analyzing wellestablished ST data of the mouse olfactory bulb(MOB),we presented a detailed view of spatial APA usage across morphological layers of the MOB.We compiled a comprehensive list of genes with spatial APA dynamics and obtained several major spatial expression patterns that represent spatial APA dynamics in different morphological layers.By extending this analysis to two additional replicates of the MOB ST data,we observed that the spatial APA patterns of several genes were reproducible among replicates.stAPAminer employs the power of ST to explore the transcriptional atlas of spatial APA patterns with spatial resolution.This toolkit is available at https://github.com/BMILAB/stAPAminer and https://ngdc.cncb.ac.cn/biocode/tools/BT007320.

中华蜜蜂泛素基因及其全长转录本的发掘及分析

旨在利用三代Nanopore测序技术发掘中华蜜蜂(Apis cerana cerana)泛素(ubiquitin)基因及其全长转录本。基于前期获得的中华蜜蜂工蜂4~6日龄幼虫肠道的全长转录组数据,使用BLAST工具将全长转录本的序列比对到KEGG和Nr数据库以鉴定泛素基因及其全长转录本。采用Astalavista软件分析泛素基因的可变剪接(alternative splicing,AS)事件,并通过RT-PCR加以验证。通过TAPIS pipeline软件分析泛素基因的可变多聚腺苷酸化(alternativepolyadenylation,APA)位点。共鉴定到48个中华蜜蜂泛素基因和435条泛素基因相关全长转录本。共发掘到48个泛素基因的74次AS事件,包括31次内含子保留事件,19次可变3′端剪接事件,16次可变5′端剪接事件及8次外显子互斥事件。RT-PCR结果证实了3种AS事件类型的真实性。共预测到38个泛素基因含有1个及以上的APA位点,并且在APA位点的上游鉴定到多个motif,一致性序列为:KCWYTDYTMWSYG MWSCARAWCCAG AATGAYCCWYWGGHWVMWGWDRTRGC。研究结果丰富了中华蜜蜂泛素基因及其全长转录本信息,为持续深入开展相关功能研究提供参考和依据。

中华蜜蜂酚氧化酶和丝氨酸蛋白酶相关基因及其全长转录本发掘与分析

为深入开展中华蜜蜂相关研究提供参考信息和基础,利用已获得的纳米孔(Nanopore)测序数据对中华蜜蜂Apis cerana cerana的酚氧化酶(phenoloxidase,PO)和丝氨酸蛋白酶(serine protease,SP)相关基因和全长转录本进行发掘和分析。通过Blast工具将中华蜜蜂所有全长转录本比对KEGG和Nr数据库以筛选出PO和SP相关基因和全长转录本。采用gffcompare软件将PO和SP相关全长转录本与东方蜜蜂参考基因组(ACSNU-2.0)已注释基因进行比较以优化结构。使用Astalavista软件鉴定PO和SP相关基因的可变剪接(alternative splicing,AS)事件,再利用IGV浏览器进行结构可视化。通过PCR验证AS事件的真实性。利用TAPIS pipeline预测和分析可变多聚腺苷酸化(alternative polyadenylation,APA)位点,并通过TBtool软件鉴定APA位点上游的基序(motif)。鉴定到中华蜜蜂PO和SP相关的42个基因与146条转录本。优化了16个参考基因组已注释PO和SP相关基因的结构,其中5′端延长和3′端延长的基因均有7个,5′端和3′端同时延长的基因有2个。鉴定到PO和SP相关的10个基因的389次AS事件,其中最丰富的AS类型是5′端可变剪接。PCR结果证实了2次AS事件的真实性。共鉴定到34个PO和SP相关基因含有1个及以上的APA位点,其中含有3个APA位点的基因数量最多;在APA位点上游鉴定到多个motif,一致性序列为:GGHKSYWSHHTRATWTCNBHDMRRYWYRTNYTVACNGCKGCDCAYTGYR。鉴定到中华蜜蜂PO和SP相关的42个基因和146条全长转录本,优化了东方蜜蜂参考基因组已注释的PO和SP相关基因结构,并发掘出PO和SP相关基因的389次AS事件和237个APA位点。

中华蜜蜂细胞吞噬与包囊作用相关基因全长转录本鉴定及分析

【目的】系统鉴定和分析中华蜜蜂(Apis cerana cerana)吞噬与包囊作用相关基因和全长转录本,为深入开展相关基因和剪接体的功能研究奠定基础。【方法】基于前期已获得的高质量中华蜜蜂纳米孔长读段测序数据,通过Blast工具将全长转录本比对Nr数据库筛选出吞噬与包囊作用相关基因和全长转录本。利用gffcompare软件将全长转录本与东方蜜蜂(Apis cerana)参考基因组上注释的转录本进行比较,鉴定未注释的新基因和新转录本。利用TAPIS pipeline预测和分析吞噬与包囊作用相关基因的可变多聚腺苷酸化(alternative polyadenylation, APA)位点,并通过TBtools软件鉴定APA位点上游的基序(motif)。使用Astalavista软件鉴定可变剪接(alternative splicing, AS)事件,并通过IGV浏览器进行结构可视化。通过RT-PCR验证AS事件的真实性。【结果】共鉴定到中华蜜蜂吞噬与包囊作用相关的基因66个和全长转录本395条,发掘出东方蜜蜂参考基因组未注释的2个新基因和303条新转录本。对参考基因组已注释的34个基因进行了结构优化,分别延伸了18个基因的5′端和12个基因的3′端,同时延长了4个基因的5′端和3′端。共鉴定到含有1个及以上APA位点的吞噬与包囊作用相关基因47个,其中多于5个APA位点的基因最多,为32个。在APA位点上游鉴定到多个基序,一致性序列为:GRBGCNKSDAACAAYTRBGCBMRNGGBYAYTAYWCNVWNGG。共鉴定到吞噬与包囊作用相关基因的AS事件296次,其中包括131次可变3′端剪接(alternative 3′splice site, A3SS)、85次内含子保留(intron retention, IR)、70次可变5′端剪接(alternative 5′splice site, A5SS)和10次外显子跳跃(exon skipping, ES)。RT-PCR结果显示,扩增的目的片段大小符合预期,证实了随机选择的2次AS事件的真实性。【结论】系统鉴定了中华蜜蜂吞噬与包囊作用相关基因和全长转录本以及AS事件和APA位点,优化了东方蜜蜂参考基因组注释的吞噬与包囊作用相关基因的结构。

基于3'RACE的胃癌细胞肿瘤相关基因的APA位点分析

目的分析胃癌细胞中肿瘤相关基因的APA(alternative polyadenylation)位点变化。方法我们选取肿瘤相关基因HSP90α和SEC11A,利用3'RACE方法在胃癌细胞系MKN45、MKN28和AGS中扩增其mRNA的3'端序列,经过测序,与已知数据库UCSC比对分析其APA位点变化。结果与正常数据库相比,胃癌细胞中HSP90α和SEC11A两个基因均出现新的APA位点,产生含有不同长度的3'UTR(untranslated region)的新mRNA异构体。结论胃癌细胞中HSP90α和SEC11A的APA位点发生变化,产生新的mRNA异构体,为研究肿瘤发生发展提供了新思路。

Aberrant Alternative Polyadenylation is Responsible for Survivin Up-regulation in Ovarian Cancer

Background： Survivin is an oncoprotein silenced in normal mature tissues but reactivated in serous ovarian cancer （SOC）. Although transcriptional activation is assumed for its overexpression, the long 3＇-untranslated region （3＇-UTR） in survivin gene, which contains many alternate polyadenylation （APA） sites, implies a propensity for posttranscriptional control and therefore was the aim of our study. Methods： The abundance of the coding region, the proximal and the distal region of survivin mRNA 3＇-UTR, was evaluated by real-time polymerase chain reaction （PCR） in SOC samples, cell lines, and normal fallopian tube （NFT） tissues. The APA sites were confirmed by rapid amplification ofcDNA 3＇ ends and DNA sequencing. Real-time PCR were used to screen survivin-targeting microRNAs （miRNAs） that were inversely correlated with survivin. The expression of an inversely correlated miRNA was restored by pre-miRNA transfection or induction with a genotoxic agent to test its inhibitory effect on survivin overexpression. Results： Varying degrees of APA were observed in SOC by comparing the abundance of the proximal and the distal region of survivin 3＇-UTR, and changes of 3＇-UTR correlated significantly with survivin expression （r = 0.708, P 〈 0.01）. The main APA sites are proved at 1197 and 1673 of survivin 3＇-UTR by DNA sequencing. Higher level of 3＇-UTR proximal region than coding region was observed in NFT, as well as in SOC and cell lines. Among the survivin-targeting miRNAs, only a few highly expressed miRNAs were inversely correlated with survivin levels, and they mainly targeted the distal part of the 3＇-UTR. However, in ovarian cancer cells, restoration of an inversely correlated miRNA （miR-34c） showed little effect on survivin expression. Conclusions： In NFT tissues, survivin is not transcriptionally silenced but regulate posttranscriptionally. In SOC, aberrant APA leads to the shortening of survivin 3＇-UTR which enables it to escape the negative regulation of miRNAs and is responsible for survivin up-regulation.

CPSF30-L-mediated recognition of mRNA m^(6)A modification controls alternative polyadenylation of nitrate signaling-related gene transcripts in Arabidopsis

N6-methyladenosine(m^(6)A),a ubiquitous internal modification of eukaryotic mRNAs,plays a vital role in almost every aspect of mRNA metabolism.However,there is little evidence documenting the role of m^(6)A in regulating alternative polyadenylation(APA)in plants.APA is controlled by a large protein-RNA complex with many components,including CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR30(CPSF30).In Arabidopsis,CPSF30 has two isoforms and the longer isoform(CPSF30-L)contains a YT512-B Homology(YTH)domain,which is unique to plants.In this study,we showed that CPSF30-L YTH domain binds to m^(6)A in v itro.In the cpsf30-2 mutant,the transcripts of many genes including several important nitrate signaling-related genes had shifts in polyadenylation sites that were correlated with m^(6)A peaks,indicating that these gene transcripts carrying m^(6)A tend to be regulated by APA.Wild-type CPSF30-L could rescue the defects in APA and nitrate metabolism in cpsf30-2,but m^(6)A-binding-defective mutants of CPSF30-L could not.Taken together,our results demonstrated that m^(6)A modification regulates APA in Arabidops is and revealed that the m^(6)A reader CPSF30-L affects nitrate signaling by controlling APA,shedding new light on the roles of the m^(6)A modification during RNA 3-end processing in nitrate metabolism.

Alternative polyadenylation of mRNA and its role in cancer

Alternative polyadenylation(APA)is a molecular process that generates diversity at the 3′end of RNA polymeraseⅡtranscripts from over 60%of human genes.APA is derived from the existence of multiple polyadenylation signals(PAS)within the same transcript,and results in the differential inclusion of sequence information at the 3′end.While APA can occur between two PASs allowing for generation of transcripts with distinct coding potential from a single gene,most APA occurs within the untranslated region(3′UTR)and changes the length and content of these non-coding sequences.APA within the 3′UTR can have tremendous impact on its regulatory potential of the mRNA through a variety of mechanisms,and indeed this layer of gene expression regulation has profound impact on processes vital to cell growth and development.Recent studies have particularly highlighted the importance of APA dysregulation in cancer onset and progression.Here,we review the current knowledge of APA and its impacts on mRNA stability,translation,localization and protein localization.We also discuss the implications of APA dysregulation in cancer research and therapy.

Alternative Polyadenylation： Methods, Findings, and Impacts

Alternative polyadenylation （APA）, a phenomenon that RNA molecules with different 3＇ ends originate from distinct polyadenylation sites of a single gene, is emerging as a mechanism widely used to regulate gene expression. In the present review, we first summarized various methods prevalently adopted in APA study, mainly focused on the next-generation sequencing （NGS）-based techniques specially designed for APA identification, the related bioinformatics methods, and the strategies for APA study in single ceils. Then we summarized the main findings and advances so far based on these methods, including the preferences of alternative polyA （pA） site, the biological processes involved, and the corresponding consequences. We especially categorized the APA changes discovered so far and discussed their potential functions under given conditions, along with the possible underlying molecular mechanisms. With more in-depth studies on extensive samples, more signatures and functions of APA will be revealed, and its diverse roles will gradually heave in sight.

OsEDM2L mediates m^(6)A of EAT1 transcript for proper alternative splicing and polyadenylation regulating rice tapetal degradation

N^(6)-methyladenosine(m^(6)A) modification affects the post-transcriptional regulation of eukaryotic gene expression, but the underlying mechanisms and their effects in plants remain largely unknown. Here,we report that the N^(6)-adenine methyltransferase-like domain-containing protein ENHANCED DOWNY MILDEW 2-LIKE(OsEDM2 L) is essential for rice(Oryza sativa L.) anther development. The osedm2 l knockout mutant showed delayed tapetal programmed cell death(PCD) and defective pollen development. OsEDM2 L interacts with the transcription factors basic helix-loop-helix 142 and TAPETUMDEGENERATIONRETARDATIONto regulate the expression of ETERNAL TAPETUM 1(EAT1), a positive regulator of tapetal PCD. Mutation of OsEDM2 L altered the transcriptomic m^(6)A landscape, and caused a distinct m^(6)A modification of the EAT1 transcript leading to dysregulation of its alternative splicing and polyadenylation, followed by suppression of the EAT1 target genes OsAP25 and OsAP37 for tapetal PCD. Therefore, OsEDM2 L is indispensable for proper messenger RNA m^(6)A modification in rice anther development.

Regulators of alternative polyadenylation operate at the transition from mitosis to meiosis

In the sexually reproductive organisms, gametes are produced by meiosis following a limited mitotic amplification. However, the intrinsic program switching cells from mitotic to meiotic cycle is unclear.Alternative polyadenylation（APA） is a highly conserved means of gene regulation and is achieved by the RNA 30-processing machinery to generate diverse 30 UTR profiles. In Drosophila spermatogenesis, we observed distinct profiles of transcriptome-wide 30 UTR between mitotic and meiotic cells. In mutant germ cells stuck in mitosis, 30 UTRs of hundreds of genes were consistently shifted. Remarkably, altering the levels of multiple 30-processing factors disrupted germline＇s progression to meiosis, indicative of APA＇s active role in this transition. An RNA-binding protein（RBP） Tut could directly bind 30 UTRs of 30-processing factors whose expressions were repressed in the presence of Tut-containing complex. Further,we demonstrated that this RBP complex could execute the repression post-transcriptionally by recruiting CCR4/Twin of deadenylation complex. Thus, we propose that an RBP complex regulates the dynamic APA profile to promote the mitosis-to-meiosis transition.

Analysis of alternative cleavage and polyadenylation in mature and differentiating neurons using RNA-seq data

Background： Most eukaryotic protein-coding genes exhibit alternative cleavage and polyadenylation （APA）, resulting in mRNA isoforms with different 3＇ untranslated regions （3＇ UTRs）. Studies have shown that brain cells tend to express long 3＇ UTR isoforms using distal cleavage and polyadenylation sites （PASs）. Methods： Using our recently developed, comprehensive PAS database PolyA_DB, we developed an efficient method to examine APA, named Significance Analysis of Alternative Polyadenylation using RNA-seq （SAAP-RS）. We applied this method to study APA in brain cells and neurogenesis. Results： We found that neurons globally express longer 3＇ UTRs than other cell types in brain, and microglia and endothelial cells express substantially shorter 3＇ UTRs. We show that the 3＇ UTR diversity across brain cells can be corroborated with single cell sequencing data. Further analysis of APA regulation of 3＇ UTRs during differentiation of embryonic stem cells into neurons indicates that a large fraction of the APA events regulated in neurogenesis are similarly modulated in myogenesis, but to a much greater extent. Conclusion： Together, our data delineate APA profiles in different brain cells and indicate that APA regulation in neurogenesis is largely an augmented process taking place in other types of cell differentiation.

Population-scale genetic control of alternative polyadenylation and its association with human diseases

Background:Genome-wide association studies(GWAS)have identified thousands of genomic non-coding variants statistically associated with many human traits and diseases,including cancer.However,the functional interpretation of these non-coding variants remains a significant challenge in the post-GWAS era.Alternative polyadenylation(APA)plays an essential role in post-transcriptional regulation for most human genes.By employing different poly(A)sites,genes can either shorten or extend the 3'-UTRs that contain cu-regulatory elements such as miRNAs or RNA-binding protein binding sites.Therefore,APA can affect the mRNA stability,translation,and cellular localization of proteins.Population-scale studies have revealed many inherited genetic variants that potentially impact APA to further influence disease susceptibility and phenotypic diversity,but systematic computational investigations to delineate the connections are in their earliest states.Results:Here,we discuss the evolving definitions of the genetic basis of APA and the modern genomics tools to identify,characterize,and validate the genetic influences of APA events in human populations.We also explore the emerging and surprisingly complex molecular mechanisms that regulate APA and summarize the genetic control of APA that is associated with complex human diseases and traits.Conclusion:APA is an intermediate molecular phenotype that can translate human common non-coding variants to individual phenotypic variability and disease susceptibility.

U1 snRNP proteins promote proximal alternative polyadenylation sites by directly interacting with 3'end processing core factors

In eukaryotic cells,both alternative splicing and alternative polyadenylation(APA)play essential roles in the gene regulation network.U1 small ribonucleoprotein particle(U1 snRNP)is a major component of spliceosome,and U1 snRNP complex can suppress proximal APA sites through crosstalking with 3end processing factors.However,here we show that both knockdown and overexpression of SNRPA,SNRPC,SNRNP70,and SNRPD2,the U1 snRNP proteins,promote the usage of proximal APA sites at the transcriptome level.SNRNP70 can drive the phase transition of PABPN1 from droplet to aggregate,which may reduce the repressive effects of PABPN1 on the proximal APA sites.Additionally,SNRNP70 can also promote the proximal APA sites by recruiting CPSF6,suggesting that the function of CPSF6 on APA is related with other RNA-binding proteins and cell context-dependent.Consequently,these results reveal that,on the contrary to U1 snRNP complex,the free proteins of U1 snRNP complex can promote proximal APA sites through the interaction with 3end processing machinery.

转录后选择性多聚腺苷酸化调控与糖尿病肾病

选择性多聚腺苷酸化(alternative polyadenylation,APA)作为重要的转录后调控机制,是真核细胞mRNA成熟过程中,由于不同多聚腺苷酸化信号位点的选择导致一个基因产生多个3’UTR序列长度不同的转录异构体,其中pre-mRNA序列中的顺式调控元件、对应的反式作用因子,例如细胞核中多种酶和蛋白因子等共同参与APA调控。研究发现,APA机制参与多种生理、病理进程,主要通过改变3’UTR序列长度影响对应反式作用因子的调控作用,进而调节mRNA定位、稳定性、翻译效率及蛋白的定位等。本文将系统阐述转录后APA的作用机制和研究现状,并结合新近研究进展,探讨APA在糖尿病肾病研究中的前景。