Project description:The quality control and export of mRNA by RNA-binding proteins are necessary for the survival of malaria parasites, which have complex life cycles. Malarial nuclear poly(A) binding protein 2 (NAB2), ALWAYS EARLY (ALY) and serine/arginine-rich (SR) proteins, such as nucleolar protein 3 (NPL3), G-strand binding protein 2 (GBP2) and SR1, are involved in nuclear mRNA export in malaria parasites. However, their functions and cellular localization are not fully understood. In this study, we found that NAB2 and SR1, but not ALY, NPL3 or GBP2, played essential roles in the asexual development of malaria parasites, while GBP2 was involved in gametocyte production. Moreover, GBP2 localized to both the nucleus and cytoplasm of malaria parasites and interacted with the proteins ALBA4, DOZI and CITH, which play roles in translational repression. Our findings suggest that malarial GBP2 may be involved in the recruitment of ALBA4, DOZI and CITH. Immunoprecipitation coupled to mass spectrometry (IP-MS) revealed that PHAX domain-containing protein, an adaptor protein for exportin-1, also interacted with GBP2, suggesting that mRNA export occurs via the PHAX domain-containing protein pathway in malaria parasites. Fluorescence live cell imaging revealed that malarial NAB2 localized at the nuclear periphery and co-localized with NUP205. Moreover, using IP-MS, we found that malarial NAB2 interacted with transportin. RNA immunoprecipitation coupled to RNA sequencing revealed that malarial NAB2 bound directly to 143 mRNAs, including those encoding 40S and 60S ribosomal proteins. This indicates that malarial NAB2 is involved in general mRNA assembly and is shuttled between the nucleus and cytoplasm. Our findings suggest that unique mRNA export and post-transcriptional gene regulation mediated by RNA-binding proteins occur in malaria parasites.
Project description:Gene expression in eukaryotes is an essential process that includes transcription, pre-RNA processing and RNA export. All these steps are coupled and normally, any failure in one step affects the other steps and could cause nuclear mRNA retention. One important player in this interface is the poly(A)-RNA binding protein Nab2, which regulates the poly(A)-tail length of mRNAs protecting their 3’-ends from a second round of polyadenylation and facilitating their nucleo-cytoplasmic export. Interestingly, here we show that Nab2 has additional roles in mRNA transcription elongation, tRNA metabolism and rRNA export. We use Genome-wide analysis of expression of a conditional degron nab2 mutant that allows the depletion of the protein in 15 minutes, to demosntrate that the role of Nab2 in RNAPII transcription and RNAPIII metabolism is not the result of a secondary effect. Our results identify primary targets of nab2 revealing novel functions for Nab2 in transcription and metabolism of most types of RNAs, not only poly(A) mRNAs, indicating that Nab2 function is more ubiquitous than previously anticipated, being a central player in the general and coordinated control of gene expression from transcription elongation to translation initiation.
Project description:Gene expression in eukaryotes is an essential process that includes transcription, pre-RNA processing and RNA export. All these steps are coupled and normally, any failure in one step affects the other steps and could cause nuclear mRNA retention. One important player in this interface is the poly(A)-RNA binding protein Nab2, which regulates the poly(A)-tail length of mRNAs protecting their 3M-bM-^@M-^Y-ends from a second round of polyadenylation and facilitating their nucleo-cytoplasmic export. Interestingly, here we show that Nab2 has additional roles in mRNA transcription elongation, tRNA metabolism and rRNA export. We use Genome-wide analysis of expression of nab2-1 mutant to demosntrate that the role of Nab2 in RNAPII transcription and RNAPIII metabolism is not the result of a secondary effect. Our results identify primary targets of nab2 revealing novel functions for Nab2 in transcription and metabolism of most types of RNAs, not only poly(A) mRNAs, indicating that Nab2 function is more ubiquitous than previously anticipated, being a central player in the general and coordinated control of gene expression from transcription elongation to translation initiation. Three repeats of the wild type and nab2-1 mutant
Project description:Gene expression in eukaryotes is an essential process that includes transcription, pre-RNA processing and RNA export. All these steps are coupled and normally, any failure in one step affects the other steps and could cause nuclear mRNA retention. One important player in this interface is the poly(A)-RNA binding protein Nab2, which regulates the poly(A)-tail length of mRNAs protecting their 3’-ends from a second round of polyadenylation and facilitating their nucleo-cytoplasmic export. Interestingly, here we show that Nab2 has additional roles in mRNA transcription elongation, tRNA metabolism and rRNA export. We use Genome-wide analysis of expression of nab2-1 mutant to demosntrate that the role of Nab2 in RNAPII transcription and RNAPIII metabolism is not the result of a secondary effect. Our results identify primary targets of nab2 revealing novel functions for Nab2 in transcription and metabolism of most types of RNAs, not only poly(A) mRNAs, indicating that Nab2 function is more ubiquitous than previously anticipated, being a central player in the general and coordinated control of gene expression from transcription elongation to translation initiation.
Project description:Gene expression in eukaryotes is an essential process that includes transcription, pre-RNA processing and RNA export. All these steps are coupled and normally, any failure in one step affects the other steps and could cause nuclear mRNA retention. One important player in this interface is the poly(A)-RNA binding protein Nab2, which regulates the poly(A)-tail length of mRNAs protecting their 3M-bM-^@M-^Y-ends from a second round of polyadenylation and facilitating their nucleo-cytoplasmic export. Interestingly, here we show that Nab2 has additional roles in mRNA transcription elongation, tRNA metabolism and rRNA export. We use Genome-wide analysis of expression of a conditional degron nab2 mutant that allows the depletion of the protein in 15 minutes, to demosntrate that the role of Nab2 in RNAPII transcription and RNAPIII metabolism is not the result of a secondary effect. Our results identify primary targets of nab2 revealing novel functions for Nab2 in transcription and metabolism of most types of RNAs, not only poly(A) mRNAs, indicating that Nab2 function is more ubiquitous than previously anticipated, being a central player in the general and coordinated control of gene expression from transcription elongation to translation initiation. Two and three repeats of the wild type control and the nab2-td mutant respectively at time 0, 30 and 75 minutes after the degron induction.
Project description:Transcription profiling was performed on the time course of Nab2 protein depletion in THC-Nab2 strain at 0h, 7h, 12h in biological triplicates to access its affect on the composition and structure of mRNA in budding yeast. For the protein depletion experiment THC-NAB2 (THJ collection Y2484, THC-NAB2:KAN tTA:URA, Open Biosystems) strain was used, where expression of the NAB2 gene is under control of a tetracyclin-repressible promoter.
Project description:The Drosophila polyadenosine RNA binding protein Nab2, which is orthologous to a human protein lost in a form of inherited intellectual disability, controls axon projection, locomotion, and memory. Here we define an unexpectedly specific role for Nab2 in regulating splicing of ~150 exons/introns in the head transcriptome and link the most prominent of these, female retention of a male-specific exon in the sex determination factor Sex-lethal (Sxl), to a role in m6A-dependent mRNA splicing. Genetic evidence indicates that aberrant Sxl splicing underlies multiple phenotypes in Nab2 mutant females. At a molecular level, Nab2 associates with Sxl pre-mRNA and ensures proper female-specific splicing by preventing m6A hypermethylation by Mettl3 methyltransferase. Consistent with these results, reducing Mettl3 expression rescues developmental, behavioral and neuroanatomical phenotypes in Nab2 mutants. Overall these data identify Nab2 as a required regulator of m6A-regulated Sxl splicing and imply a broader link between Nab2 and Mettl3-regulated brain RNAs.