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: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.

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.

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.

SIZ1-mediated SUMOylation of CPSF100 promotes plant thermomorphogenesis by controlling alternative polyadenylation

Under warm temperatures,plants adjust their morphologies for environmental adaption via precise gene expression regulation.However,the function and regulation of alternative polyadenylation(APA),an important fine-tuning of gene expression,remains unknown in plant thermomorphogenesis.In this study,we found that SUMOylation,a critical post-translational modification,is induced by a long-term treat-ment at warm temperatures via a SUMO ligase SIZ1 in Arabidopsis.Disruption of SIZ1 altered the global usage of polyadenylation signals and affected the APA dynamic of thermomorphogenesis-related genes.CPSF100,a key subunit of the CPSF complex for polyadenylation regulation,is SUMOylated by SIZ1.Importantly,we demonstrated that SUMOylation is essential for the function of CPSF1oo in genome-wide polyadenylation site choice during thermomorphogenesis.Further analyses revealed that the SUMO conjugation on CPSF100 attenuates its interaction with two isoforms of its partner CPSF30,increasing the nuclear accumulation of CPsF1oo for polyadenylation regulation.In summary,our study uncovers a regulatory mechanism of APA via SiZ1-mediated SUMOylation in plant thermomorpho-genesis.

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.

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.

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.

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.

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.

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.

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.

The polyadenylation code:a unified model for the regulation of mRNA alternative polyadenylation

The majority of eukaryotic genes produce multiple mRNA isoforms with distinct 3＇ ends through a process called mRNA alternative polyadenylation （APA）. Recent studies have demonstrated that APA is dynamically regulated during development and in response to environmental stimuli. A number of mechanisms have been described for APA regulation. In this review, we attempt to integrate all the known mechanisms into a unified model. This model not only explains most of previous results, but also provides testable predictions that will improve our understanding of the mechanistic details of APA regulation. Finally, we briefly discuss the known and putative functions of APA regulation.

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.

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.

Stress responses of plants through transcriptome plasticity by mRNA alternative polyadenylation

The sessile nature of plants confines their responsiveness to changing environmental conditions.Gene expression regulation becomes a paramount mechanism for plants to adjust their physiological and morphological behaviors.Alternative polyadenylation(APA)is known for its capacity to augment transcriptome diversity and plasticity,thereby furnishing an additional set of tools for modulating gene expression.APA has also been demonstrated to exhibit intimate associations with plant stress responses.In this study,we review APA dynamic features and consequences in plants subjected to both biotic and abiotic stresses.These stresses include adverse environmental stresses,and pathogenic attacks,such as cadmium toxicity,high salt,hypoxia,oxidative stress,cold,heat shock,along with bacterial,fungal,and viral infections.We analyzed the overarching research framework employed to elucidate plant APA response and the alignment of polyadenylation site transitions with the modulation of gene expression levels within the ambit of each stress condition.We also proposed a general APA model where transacting factors,including poly(A)factors,epigenetic regulators,RNA m6A modification factors,and phase separation proteins,assume pivotal roles in APA related transcriptome plasticity during stress response in plants.

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.

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.

Emerging applications of catalytically inactive CRISPR-Cas13 system in mRNA engineering

Posttranscriptional regulations of different types of RNA,including rRNA,tRNA,mRNA and ncRNA are widely involved in normal physiology and diseases.m RNA,as the intermediary product between gene and protein,whose posttranscriptional regulations such as alternative splicing,alternative polyadenylation and modifications impact its coded protein expression and functions.However,the functional significance and therapeutic potential of RNA posttranscriptional regulations are not well studied due to the lack of suitable RNA engineering platforms.The discovery of a novel CRISPR-Cas system termed CRISPR-Cas13 in 2015 that specifically targets RNA templates brought a new role to CRISPR to target and edit RNA with high specificity,which opened a new era of RNA manipulations to some degree.This review will summarize the emerging applications of the catalytically inactive CRISPR-Cas13 system(CRISPR-dCas13)in mRNA engineering and highlight the prospection of the CRISPR-dCas13 system for other RNA modification regulations and its therapeutic potential.

Down-regulated expression of atypical PKC-binding domain deleted asip isoforms in human hepatocellular carcinomas

Asip is a mammalian homologue of polarity protein Par-3 of Caenorhabditis elegans and Bazooka of Drosophila melanogaster. Asip/Par-3/Bazooka are PDZ-motif containing proteins that localize asymmetrically to the cell periphery and play a pivotal role in cell polarity and asymmetric cell division. In the present study, we have cloned human asip cDNA and its splicing variants by 5’-RACE and RT-PCR using candidate human EST clones which have a high homology to rat asip cDNA. The full-length cDNA of human asip encodes a 1,353 aa protein exhibiting 88% similarity to the rat one. Human asip is a single copy gene consisting of at least 26 exons and localizing in human chromosome 10, band p11.2, with some extraordinarily long introns. All exon/intron boundary nucleotides conform to the "gt-ag" rule. Three main transcripts were detected by Northern blot analysis, and at least five variants, from alternative splicing and polyadenylation, have been identified by RT-PCR and liver cDNA library screening. Exon 17b deleted asip mRNAs expressed ubiquitously in normal human tissues, including liver, on RT-PCR analysis. However, they were absent from most human liver cancer cell lines examined. More interestingly, the expression of exon 1 7b deleted variants was down regulated in 52.6% (10/19) clinic specimens of human hepatocellular carcinomas (HCCs), compared with the surrounding nontumorous liver tissues from the same patients. The presence of various splicing transcripts, the variation of their distribution among different tissues and cells, and their differential expressions in human HCCs suggest that human Asip isoforms may function in different context.