<i>Arabidopsis</i>Floral Initiator SKB1 Confers High Salt Tolerance by Regulating Transcription and Pre-mRNA Splicing through Altering Histone H4R3 and Small Nuclear Ribonucleoprotein LSM4 Methylation

Growing evidence suggests that core spliceosomal components differentially affect RNA processing of specific genes; however, whether changes in the levels or activities of these factors control specific signaling pathways is largely unknown. Here we show that some SM-like (LSM) genes, which encode core components of the spliceosomal U6 small nuclear ribonucleoprotein complex, regulate circadian rhythms in plants and mammals. We found that the circadian clock regulates the expression of LSM5 in Arabidopsis plants and several LSM genes in mouse suprachiasmatic nucleus. Further, mutations in LSM5 or LSM4 in Arabidopsis, or down-regulation of LSM3, LSM5, or LSM7 expression in human cells, lengthens the circadian period. Although we identified changes in the expression and alternative splicing of some core clock genes in Arabidopsis lsm5 mutants, the precise molecular mechanism causing period lengthening remains to be identified. Genome-wide expression analysis of either a weak lsm5 or a strong lsm4 mutant allele in Arabidopsis revealed larger effects on alternative splicing than on constitutive splicing. Remarkably, large splicing defects were not observed in most of the introns evaluated using RNA-seq in the strong lsm4 mutant allele used in this study. These findings support the idea that some LSM genes play both regulatory and constitutive roles in RNA processing, contributing to the fine-tuning of specific signaling pathways.posttranscriptional | alternative splicing | circadian clock | Arabidopsis | mammals C ircadian rhythms are persistent 24-h oscillations in biological processes that occur under constant environmental conditions. They allow organisms to coordinate multiple physiological processes with periodic or seasonal changes that occur in the environment. At the heart of the eukaryotic circadian system lies a complex set of interconnected transcriptional and translational feedback loops, in which a group of core clock genes regulate each other to ensure that their mRNA levels oscillate with a period of ∼24 h (1). The core oscillator in Arabidopsis thaliana involves two MYB domain-containing transcription factors, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), that repress the expression of TIMING OF CAB2 EXPRESSION 1 (TOC1) at the beginning of the day. In turn, TOC1, a member of the PSEUDO-RESPONSE REGULATOR (PRR) family, represses CCA1/LHY expression at the end of the day (2). Other clock components expressed throughout the day form multiple interconnected transcriptional feedback loops (2).Mounting evidence indicates that alternative splicing (AS), the process by which pre-mRNA molecules are differentially spliced to yield multiple mRNA isoforms from a single gene, plays a key role in the regulation of circadian networks in a variety of organisms, including Drosophila melanogaster (3), Neurospora crassa (4-6), and Arabidopsis (7-11). For example, the core clock genes period in Drosophila and frequency in Neurospora give rise to different mRNA isoforms through AS, which helps t...

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“…S8B). These findings are consistent with the alterations in abiotic stress responses present in both sad1/lsm5 and lsm4 mutants (28,31).…”

Section: A Mutation In Arabidopsis Lsm5 Confers a Long Period Phenotysupporting

confidence: 89%

Role for LSM genes in the regulation of circadian rhythms

Perez-Santángelo

Mancini

Francey

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…AtPRMT5, the Arabidopsis homolog of PRMT5, regulates multiple aspects of plant growth and development, such as flowering time, growth rate, leaf morphology, sensitivity to stress conditions, and circadian rhythm, by modulating transcription, constitutive and alternative precursor mRNA (pre-mRNA) splicing of diverse genes (9)(10)(11)(12)(13). AtPRMT5 also mediates the symmetric arginine dimethylation of uridine-rich small nuclear ribonucleoproteins (U snRNPs) AtSmD1, D3, and AtLSm4 proteins, thus linking arginine methylation and splicing (10,11,13). However, the exact mechanism remains elusive.…”

mentioning

confidence: 99%

Recruitment of the NineTeen Complex to the activated spliceosome requires AtPRMT5

Deng

Wang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Protein arginine methylation, catalyzed by protein arginine methyltransferases (PRMTs), is involved in a multitude of biological processes in eukaryotes. Symmetric arginine dimethylation mediated by PRMT5 modulates constitutive and alternative pre-mRNA splicing of diverse genes to regulate normal growth and development in multiple species; however, the underlying molecular mechanism remains largely unknown. A genetic screen for suppressors of an Arabidopsis symmetric arginine dimethyltransferase mutant, atprmt5, identified two gain-of-function alleles of pre-mRNA processing factor 8 gene (prp8-8 and prp8-9), the highly conserved core component of the U5 small nuclear ribonucleoprotein (snRNP) and the spliceosome. These two atprmt5 prp8 double mutants showed suppression of the developmental and splicing alterations of atprmt5 mutants. In atprmt5 mutants, the NineTeen complex failed to be assembled into the U5 snRNP to form an activated spliceosome; this phenotype was restored in the atprmt5 prp8-8 double mutants. We also found that loss of symmetric arginine dimethylation of Sm proteins prevents recruitment of the NineTeen complex and initiation of spliceosome activation. Together, our findings demonstrate that symmetric arginine dimethylation has important functions in spliceosome assembly and activation, and uncover a key molecular mechanism for arginine methylation in pre-mRNA splicing that impacts diverse developmental processes.arginine methylation | protein arginine methyltransferase | AtPRMT5 | pre-mRNA splicing | Prp19C/NTC P rotein arginine methyltransferase 5 (PRMT5), a highly conserved type II protein arginine methyltransferase, transfers methyl groups to arginine residues, generating monomethylarginine and symmetric ω-N G , N′ G -dimethylarginine (SDMA) (1-3). In mammals, PRMT5 methylates and interacts with diverse proteins, including histones and other proteins, and has long been implicated in the modulation of a variety of processes, such as transcriptional regulation, RNA metabolism (4), apoptosis (5), signal transduction (6), and germ cell development (7). Both loss-of-function and overexpression of PRMT5 are fatal in mammals (8). AtPRMT5, the Arabidopsis homolog of PRMT5, regulates multiple aspects of plant growth and development, such as flowering time, growth rate, leaf morphology, sensitivity to stress conditions, and circadian rhythm, by modulating transcription, constitutive and alternative precursor mRNA (pre-mRNA) splicing of diverse genes (9-13). AtPRMT5 also mediates the symmetric arginine dimethylation of uridine-rich small nuclear ribonucleoproteins (U snRNPs) AtSmD1, D3, and AtLSm4 proteins, thus linking arginine methylation and splicing (10,11,13). However, the exact mechanism remains elusive.Pre-mRNA splicing occurs in the nucleus, removing introns and ligating exons (14). In eukaryotes, most introns are spliced in a series of reactions catalyzed by the spliceosome, which consists of five subcomplexes of U snRNPs and several non-snRNP factors. Each U snRNP contains distinct splicing...

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“…Misexpression of several splicing regulators alters flowering time (Lopato et al, 1999;Ali et al, 2007;Streitner et al, 2010;Zhang et al, 2011). Similarly, when transcriptome changes were monitored in Arabidopsis plants transferred from 16 to 25°C, leading to accelerated flowering via the ambient temperature pathway, RNA processing-related factors were enriched .…”

Section: Flowering Timementioning

confidence: 99%

Alternative Splicing at the Intersection of Biological Timing, Development, and Stress Responses

2013

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High-throughput sequencing for transcript profiling in plants has revealed that alternative splicing (AS) affects a much higher proportion of the transcriptome than was previously assumed. AS is involved in most plant processes and is particularly prevalent in plants exposed to environmental stress. The identification of mutations in predicted splicing factors and spliceosomal proteins that affect cell fate, the circadian clock, plant defense, and tolerance/sensitivity to abiotic stress all point to a fundamental role of splicing/AS in plant growth, development, and responses to external cues. Splicing factors affect the AS of multiple downstream target genes, thereby transferring signals to alter gene expression via splicing factor/AS networks. The last two to three years have seen an ever-increasing number of examples of functional AS. At a time when the identification of AS in individual genes and at a global level is exploding, this review aims to bring together such examples to illustrate the extent and importance of AS, which are not always obvious from individual publications. It also aims to ensure that plant scientists are aware that AS is likely to occur in the genes that they study and that dynamic changes in AS and its consequences need to be considered routinely.

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ArabidopsisFloral Initiator SKB1 Confers High Salt Tolerance by Regulating Transcription and Pre-mRNA Splicing through Altering Histone H4R3 and Small Nuclear Ribonucleoprotein LSM4 Methylation

Cited by 167 publications

References 104 publications

Role for LSM genes in the regulation of circadian rhythms

Role for LSM genes in the regulation of circadian rhythms

Recruitment of the NineTeen Complex to the activated spliceosome requires AtPRMT5

Alternative Splicing at the Intersection of Biological Timing, Development, and Stress Responses

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