Project description:General discard pathways eliminate unprocessed and irregular pre-mRNAs to control the quality of gene expression. In contrast to such general pre-mRNA decay, we describe here a nuclear pre-mRNA degradation pathway that controls the expression of select intron-containing genes. We show that the fission yeast nuclear poly(A)-binding protein, Pab2, and the nuclear exosome subunit, Rrp6, are the main factors involved in this polyadenylation-dependent pre-mRNA degradation pathway. Transcriptome analysis and intron swapping experiments revealed that inefficient splicing is important to dictate susceptibility to Pab2-dependent pre-mRNA decay. We also show that negative splicing regulation can promote the poor splicing efficiency required for this pre-mRNA decay pathway, and in doing so identify a mechanism of cross-regulation between paralogous ribosomal proteins through nuclear pre-mRNA decay. Our findings unveil a layer of regulation in the nucleus in which the turnover of specific pre-mRNAs, besides the turnover of mature mRNAs, is used to control gene expression.
Project description:In plants, many gene transcripts are very unstable, which is important for the tight control of their temporal and spatial expression patterns. To identify cellular factors controlling the stability of unstable mRNAs in plants, we used luciferase imaging in Arabidopsis to isolate a recessive mutant, stabilized 1 (sta1), with enhanced stability of the normally unstable luciferase transcript. The sta1 mutation also causes the stabilization of some endogenous gene transcripts and has a range of developmental and stress response phenotypes. STA1 encodes a nuclear protein similar to the human U5 snRNP-associated 102-kDa protein and to the yeast pre-mRNA splicing factor Prp1p and Prp6p. STA1 expression is up-regulated by cold stress, and the sta1 mutant is defective in the splicing of the cold-induced COR15A gene. Our results show that STA1 is a pre-mRNA splicing factor required for not only splicing but also the turnover of unstable transcripts and that it has an important role in plant responses to abiotic stresses. Experiment Overall Design: Five replicates for WT (Control) and two replicates for sta1 (mutant) were compared.
Project description:In plants, many gene transcripts are very unstable, which is important for the tight control of their temporal and spatial expression patterns. To identify cellular factors controlling the stability of unstable mRNAs in plants, we used luciferase imaging in Arabidopsis to isolate a recessive mutant, stabilized 1 (sta1), with enhanced stability of the normally unstable luciferase transcript. The sta1 mutation also causes the stabilization of some endogenous gene transcripts and has a range of developmental and stress response phenotypes. STA1 encodes a nuclear protein similar to the human U5 snRNP-associated 102-kDa protein and to the yeast pre-mRNA splicing factor Prp1p and Prp6p. STA1 expression is up-regulated by cold stress, and the sta1 mutant is defective in the splicing of the cold-induced COR15A gene. Our results show that STA1 is a pre-mRNA splicing factor required for not only splicing but also the turnover of unstable transcripts and that it has an important role in plant responses to abiotic stresses. Keywords: Genetic Modification
Project description:In plants, pre-mRNA alternative splicing has been demonstrated to be a crucial tier that regulates gene expression in response to salt stress. However, the underlying mechanisms remain elusive. Here, we studied the roles of DIGEORGE-SYNDROME CRITICAL REGION 14-like (AtDGCR14L) in regulating pre-mRNA splicing and salt stress tolerance. We discovered that Arabidopsis AtDGCR14L is required for maintaining plant salt stress tolerance and the constitutively spliced and active isoforms of important stress- and/or abscisic acid (ABA)-responsive genes. We also identified the interaction between AtDGCR14L and splicing factor U1-70k, which needs a highly conserved three amino acid (TWG) motif in DGCR14. Different from wild-type AtDGCR14L, the overexpression of the TWG-substituted AtDGCR14L mutant did not change salt stress tolerance or pre-mRNA splicing of stress/ABA-responsive genes. Additionally, SWITCH3A (SWI3A) is a core subunit of the SWI/SUCROSE NONFERMENTING (SWI/SNF) chromatin-remodeling complexes. We found that SWI3A, whose splicing depends on AtDGCR14L, actively enhances salt stress tolerance. These results revealed that AtDGCR14L may play an essential role in crosstalk between plant salt-stress response and pre-mRNA splicing mechanisms. We also unveiled the potential role of SWI3A in controlling salt stress tolerance. The TWG motif in the intrinsically disordered region of AtDGCR14L is highly conserved and crucial for DGCR14 functions.
Project description:Salt stress caused by soil salination inhibits plant growth and development that result in reduction of crop yield and threaten the food security. Several spliceosome components are considered to modify salt stress responses in plants. However, the molecular basis of spliceosome proteins adjustment to salt stress is still unclear. Here we report that an Sm core protein SmEb is required for salt tolerance in Arabidopsis. In addition, SmEb controls alternative splicing of hundreds of pre-mRNA to participate in plant response to salt stress. Our results further reveal that SmEb takes effect on maintain proper ratio of two RCD1 splicing variants to adjust to H2O2 accumulation under salt stress. Together, our findings uncover that proper alternative splicing of pre-mRNAs governed by the spliceosome component SmEb is essential for plant salt stress responses. Salt stress caused by soil salination inhibits plant growth and development that result in reduction of crop yield and threaten the food security. Several spliceosome components are considered to modify salt stress responses in plants. However, the molecular basis of spliceosome proteins adjustment to salt stress is still unclear. Here we report that an Sm core protein SmEb is required for salt tolerance in Arabidopsis. In addition, SmEb controls alternative splicing of hundreds of pre-mRNA to participate in plant response to salt stress. Our results further reveal that SmEb takes effect on maintain proper ratio of two RCD1 splicing variants to adjust to H2O2 accumulation under salt stress. Together, our findings uncover that proper alternative splicing of pre-mRNAs governed by the spliceosome component SmEb is essential for plant salt stress responses.
Project description:To investigate the possible range of additional RNase P substrates in vivo a strand-specific, high-density microarray was used to analyze what RNA accumulates with a mutation in the catalytic RNA subunit of nuclear RNase P in Saccharomyces cerevisiae. A wide variety of noncoding RNAs were shown to accumulate, suggesting nuclear RNase P participates in the turnover of normally unstable nuclear RNAs. In some cases, the accumulated noncoding RNAs were shown to be antisense to transcripts that commensurately decreased in abundance. Pre-mRNAs containing introns also accumulated broadly, consistent with either compromised splicing or failure to efficiently turnover pre-mRNAs that do not enter the splicing pathway. Taken together with the high complexity of the nuclear RNase P holoenzyme and its relatively non-specific capacity to bind and cleave mixed sequence RNAs, these data suggest nuclear RNase P facilitates turnover of nuclear RNAs in addition to its role in pre-tRNA biogenesis.
Project description:Current models posit that nuclear speckles (NSs) serve as reservoirs of splicing factors and facilitate post-transcriptional processing of mRNA. Here, we discovered that ribotoxic stress leads to a profound reorganization of NSs with enhanced recruitment of factors required for 5' and 3' splice site recognition including the RNA-binding protein TIAR, U1 snRNP proteins and U2-associated factor 65, as well as serine 2 phosphorylated RNA polymerase II. NS reorganization is dependent on the stress-activated p38 mitogen activated protein kinase (MAPK), and goes along with splicing activation of both pre-existing and nascent pre-mRNAs. In particular, ribotoxic stress causes targeted excision of retained introns from pre-mRNAs of immediate early genes (IEGs), whose transcription is induced during the stress response. Importantly, enhanced splicing of the IEGs ZFP36 and FOS is accompanied by re-localization of the corresponding mRNAs to NSs. Our study reveals NSs as a dynamic compartment that is remodeled under stress conditions to promote the excision of retained introns and thereby enhance the expression and processing of IEG mRNAs.
Project description:Current models posit that nuclear speckles (NSs) serve as reservoirs of splicing factors and facilitate post-transcriptional processing of mRNA. Here, we discovered that ribotoxic stress leads to a profound reorganization of NSs with enhanced recruitment of factors required for 5' and 3' splice site recognition including the RNA-binding protein TIAR, U1 snRNP proteins and U2-associated factor 65, as well as serine 2 phosphorylated RNA polymerase II. NS reorganization is dependent on the stress-activated p38 mitogen activated protein kinase (MAPK), and goes along with splicing activation of both pre-existing and nascent pre-mRNAs. In particular, ribotoxic stress causes targeted excision of retained introns from pre-mRNAs of immediate early genes (IEGs), whose transcription is induced during the stress response. Importantly, enhanced splicing of the IEGs ZFP36 and FOS is accompanied by re-localization of the corresponding mRNAs to NSs. Our study reveals NSs as a dynamic compartment that is remodeled under stress conditions to promote the excision of retained introns and thereby enhance the expression and processing of IEG mRNAs.
Project description:Current models posit that nuclear speckles (NSs) serve as reservoirs of splicing factors and facilitate post-transcriptional processing of mRNA. Here, we discovered that ribotoxic stress leads to a profound reorganization of NSs with enhanced recruitment of factors required for 5' and 3' splice site recognition including the RNA-binding protein TIAR, U1 snRNP proteins and U2-associated factor 65, as well as serine 2 phosphorylated RNA polymerase II. NS reorganization is dependent on the stress-activated p38 mitogen activated protein kinase (MAPK), and goes along with splicing activation of both pre-existing and nascent pre-mRNAs. In particular, ribotoxic stress causes targeted excision of retained introns from pre-mRNAs of immediate early genes (IEGs), whose transcription is induced during the stress response. Importantly, enhanced splicing of the IEGs ZFP36 and FOS is accompanied by re-localization of the corresponding mRNAs to NSs. Our study reveals NSs as a dynamic compartment that is remodeled under stress conditions to promote the excision of retained introns and thereby enhance the expression and processing of IEG mRNAs.
Project description:Cold stress resulting from chilling and freezing temperatures substantially inhibits plant growth and reduces crop production worldwide. Tremendous research efforts have been focused on elucidating the molecular mechanisms of freezing tolerance in plants. Little is known about the molecular nature of chilling stress responses in plants. Here we found that two allelic mutants in a spliceosome component gene SmEb (smeb-1 and smeb-2) are defective in development and responses to chilling stress. RNA-seq analysis revealed that SmEb controls the splicing of many pre-mRNAs under chilling stress. The intron retentive COP1b splicing variant was dramatically induced by chilling stress in the smeb mutants. This nuclear-depleted COP1b lacks the nuclear speckle-localization capacity, supporting the regulatory role of COP1-HY5 interaction in hypocotyl elongation during chilling stress. Genetic evidence indicates that chilling-sensitive phenotype of the smeb mutants are partially rescued by the hy5 mutation. The transcription factor BES1 shows a dramatic defect in pre-mRNA splicing in the smeb mutants. Ectopic expression of the two BES1 splicing variants enhances the chilling sensitivity of the smeb-1 mutant. Biochemical and genetic analysis showed that CBFs act as negative upstream regulators of SmEb by directly suppressing its transcription. Together, our results demonstrate that proper alternative splicing of pre-mRNAs controlled by the spliceosome component SmEb is critical for plant development and chilling stress responses. Cold stress resulting from chilling and freezing temperatures substantially inhibits plant growth and reduces crop production worldwide. Tremendous research efforts have been focused on elucidating the molecular mechanisms of freezing tolerance in plants. Little is known about the molecular nature of chilling stress responses in plants. Here we found that two allelic mutants in a spliceosome component gene SmEb (smeb-1 and smeb-2) are defective in development and responses to chilling stress. RNA-seq analysis revealed that SmEb controls the splicing of many pre-mRNAs under chilling stress. The intron retentive COP1b splicing variant was dramatically induced by chilling stress in the smeb mutants. This nuclear-depleted COP1b lacks the nuclear speckle-localization capacity, supporting the regulatory role of COP1-HY5 interaction in hypocotyl elongation during chilling stress. Genetic evidence indicates that chilling-sensitive phenotype of the smeb mutants are partially rescued by the hy5 mutation. The transcription factor BES1 shows a dramatic defect in pre-mRNA splicing in the smeb mutants. Ectopic expression of the two BES1 splicing variants enhances the chilling sensitivity of the smeb-1 mutant. Biochemical and genetic analysis showed that CBFs act as negative upstream regulators of SmEb by directly suppressing its transcription. Together, our results demonstrate that proper alternative splicing of pre-mRNAs controlled by the spliceosome component SmEb is critical for plant development and chilling stress responses.