Project description:Recent transcriptome analysis indicates that >90% of human genes undergoes alternative splicing, underscoring the contribution of differential RNA processing to diverse proteomes in higher eukaryotic cells. The polypyrimidine tract binding protein PTB is a well-characterized splicing repressor, but PTB knockdown causes both exon inclusion and skipping. Genome-wide mapping of PTB-RNA interactions and construction of a functional RNA map now revealed that dominant PTB binding near a competing constitutive splice site generally induces exon inclusion whereas prevalent binding close to an alternative site often causes exon skipping. This positional effect was further demonstrated by disrupting or creating a PTB binding site on minigene constructs and testing their responses to PTB knockdown or overexpression. These findings suggest a mechanism for PTB to modulate splice site competition to produce opposite functional consequences, which may be generally applicable to RNA binding splicing factors to positively or negatively regulate alternative splicing in mammalian cells.
Project description:Recent transcriptome analysis indicates that >90% of human genes undergoes alternative splicing, underscoring the contribution of differential RNA processing to diverse proteomes in higher eukaryotic cells. The polypyrimidine tract binding protein PTB is a well-characterized splicing repressor, but PTB knockdown causes both exon inclusion and skipping. Genome-wide mapping of PTB-RNA interactions and construction of a functional RNA map now revealed that dominant PTB binding near a competing constitutive splice site generally induces exon inclusion whereas prevalent binding close to an alternative site often causes exon skipping. This positional effect was further demonstrated by disrupting or creating a PTB binding site on minigene constructs and testing their responses to PTB knockdown or overexpression. These findings suggest a mechanism for PTB to modulate splice site competition to produce opposite functional consequences, which may be generally applicable to RNA binding splicing factors to positively or negatively regulate alternative splicing in mammalian cells. Examination of PTB-RNA binding in Hela cells using CLIP-seq (Cross-Linking ImmunoPrecipitation coupled with high-throughput sequencing) method. Peaks: The four alignment files (linked as supplementary files on Sample records) were combined together for peak finding, as we found that most of the monomeric and dimeric tags are similarly distributed in the genome with high pearson correlation coefficient. The method to detect the peaks above gene-specific randomized background was similar to (Yeo et al., 2009) and described in the paper (Xue et al., 2009).
Project description:The purpose of the study was to determine proteins that specially interact cytoplasmic PTB. PTB is an RNA binding protein that shuttles between the nucleus and cytoplasm. To identified proteins interacting with cytoplasmic PTB, nucleus localization signal was deleted (PTB ΔNLS-GFP) and overexpressed followed by IP and MS.
Project description:The combination therapy of the Artemisinin-derivative Artemether (ART) with Lumefantrine (LM) (Coartem®) is an important malaria treatment regimen in many endemic countries. Resistance to Artemisinin has already been reported, and it is feared that LM resistance (LMR) could also evolve quickly. Therefore molecular markers which can be used to track Coartem®efficacy are urgently needed. Often, stable resistance arises from initial, unstable phenotypes that can be identified in vitro. Here we have used the Plasmodium falciparum multidrug resistant reference strain V1S to induce LMR in vitro by culturing the parasite under continuous drug pressure for 16 months. The initial IC50 (inhibitory concentration that kills 50% of the parasite population) was 24 nM. The resulting resistant strain V1SLM, obtained after culture for an estimated 166 cycles under LM pressure, grew steadily in 378 nM of LM; this corresponds to 15 times the IC50 of the parental strain. However, after two weeks of culturing V1SLM in drug-free medium, the IC50 returned to that of the initial, parental strain V1S. This transient drug tolerance was associated with major changes in gene expression profiles: when we explored V1SLM using the PFSANGER Affymetrix custom array, we identified 184 differentially expressed (DE) genes; amongst those 18 putative transporters including the multidrug resistance gene (pfmdr1), the multidrug resistance associated protein (pfmrp1) and the V-type H+ pumping pyrophosphatase 2 (pfvp2). Moreover, our results showed significant enrichment of genes associated with fatty acid metabolism and a clear selective advantage for two genomic loci in parasites grown under LM drug pressure, suggesting these genes may contribute to LM response in P. falciparum and could prove useful as molecular markers to monitor LM susceptibility.