Spatial mapping of splicing factor complexes involved in exon and intron definition

We have analyzed the interaction between serine/arginine-rich (SR) proteins and splicing components that recognize either the 5′ or 3′ splice site. Previously, these interactions have been extensively characterized biochemically and are critical for both intron and exon definition. We use fluorescence resonance energy transfer (FRET) microscopy to identify interactions of individual SR proteins with the U1 small nuclear ribonucleoprotein (snRNP)–associated 70-kD protein (U1 70K) and with the small subunit of the U2 snRNP auxiliary factor (U2AF35) in live-cell nuclei. We find that these interactions occur in the presence of RNA polymerase II inhibitors, demonstrating that they are not exclusively cotranscriptional. Using FRET imaging by means of fluorescence lifetime imaging microscopy (FLIM), we map these interactions to specific sites in the nucleus. The FLIM data also reveal a previously unknown interaction between HCC1, a factor related to U2AF65, with both subunits of U2AF. Spatial mapping using FLIM-FRET reveals differences in splicing factors interactions within complexes located in separate subnuclear domains

Splicing functional analysis of DNA variants within the breast cancer type 2 susceptibility gene (BRCA2), and its effect on hereditary breast and ovarian cancaer (HBOC): A hybrid minigene approach

We aim to assess exon 17 splicing variants involvement in the genetic susceptibility to HBOC, by a bioinformatic analysis and mRNA functional assays through a hybrid minigene strategy. 1) To select the candidate variants of the functional analysis based on a bioinformatic prediction, using online databases as BIC and algorithms as the presented on the Human Splicing Finder Database (HSF). 2) To construct and validate a wild type minigene that contains the 14-20 exons of BRCA2 and can be used as a vector of the functional analysis. 3) To generate each of the selected BRCA2 variants within the minigene. 4) To perform a functional analysis of the variants (driven in eukaryote cells), in order to evaluate its effect on the mRNA splicing. 5) To characterize the new-generated splicing patterns. 6) To contribute to the understanding of the HBOC genetic predisposition spectrum.Máster en Investigación Biomédic

cDNA Cloning Demonstrates the Expression of Pregnancy-Specific Glycoprotein Genes, a Subgroup of the Carcinoembryonic Antigen Gene Family, in Fetal Liver

The pregnancy-specific glycoprotein (PSG) genes constitute a subgroup of the carcinoembryonic antigen (CEA) gene family. Here we report the cloning of four cDNAs coding for different members of the PSG family from a human fetal liver cDNA library. They are derived from three closely related genes (PSG1, PSG4 and PSG6). Two of the cDNA clones represent splice variants of PSG1 (PSG1a, PSG1d) differing in their C-terminal domain and 3′-untranslated regions. All encoded proteins show the same domain arrangement (N-RA1-RA2-RB2-C). Transcripts of the genes PSG1 and PSG4 could be detected in placenta by hybridization with gene-specific oligonucleotides. Expression of cDNA in a mouse and monkey cell line shows that the glycosylated PSG1a protein has a Mr of 65–66 kD and is released from the transfected cells. Sequence comparisons in the C-terminal domain and the 3′-untranslated regions of CEA/PSG-like genes suggests a complex splicing pattern to exist for various gene family members and a common evolutionary origin of these region

Fast splice site detection using information content and feature reduction

Background: Accurate identification of splice sites in DNA sequences plays a key role in the prediction of gene structure in eukaryotes. Already many computational methods have been proposed for the detection of splice sites and some of them showed high prediction accuracy. However, most of these methods are limited in terms of their long computation time when applied to whole genome sequence data. Results: In this paper we propose a hybrid algorithm which combines several effective and informative input features with the state of the art support vector machine (SVM). To obtain the input features we employ information content method based on Shannon\u27s information theory, Shapiro\u27s score scheme, and Markovian probabilities. We also use a feature elimination scheme to reduce the less informative features from the input data. Conclusion: In this study we propose a new feature based splice site detection method that shows improved acceptor and donor splice site detection in DNA sequences when the performance is compared with various state of the art and well known method

Predicting the Impact of Alternative Splicing on Plant MADS Domain Protein Function

Several genome-wide studies demonstrated that alternative splicing (AS) significantly increases the transcriptome complexity in plants. However, the impact of AS on the functional diversity of proteins is difficult to assess using genome-wide approaches. The availability of detailed sequence annotations for specific genes and gene families allows for a more detailed assessment of the potential effect of AS on their function. One example is the plant MADS-domain transcription factor family, members of which interact to form protein complexes that function in transcription regulation. Here, we perform an in silico analysis of the potential impact of AS on the protein-protein interaction capabilities of MIKC-type MADS-domain proteins. We first confirmed the expression of transcript isoforms resulting from predicted AS events. Expressed transcript isoforms were considered functional if they were likely to be translated and if their corresponding AS events either had an effect on predicted dimerisation motifs or occurred in regions known to be involved in multimeric complex formation, or otherwise, if their effect was conserved in different species. Nine out of twelve MIKC MADS-box genes predicted to produce multiple protein isoforms harbored putative functional AS events according to those criteria. AS events with conserved effects were only found at the borders of or within the K-box domain. We illustrate how AS can contribute to the evolution of interaction networks through an example of selective inclusion of a recently evolved interaction motif in the MADS AFFECTING FLOWERING1-3 (MAF1–3) subclade. Furthermore, we demonstrate the potential effect of an AS event in SHORT VEGETATIVE PHASE (SVP), resulting in the deletion of a short sequence stretch including a predicted interaction motif, by overexpression of the fully spliced and the alternatively spliced SVP transcripts. For most of the AS events we were able to formulate hypotheses about the potential impact on the interaction capabilities of the encoded MIKC protein

Alternative Splicing at a NAGNAG Acceptor Site as a Novel Phenotype Modifier

Approximately 30% of alleles causing genetic disorders generate premature termination codons (PTCs), which are usually associated with severe phenotypes. However, bypassing the deleterious stop codon can lead to a mild disease outcome. Splicing at NAGNAG tandem splice sites has been reported to result in insertion or deletion (indel) of three nucleotides. We identified such a mechanism as the origin of the mild to asymptomatic phenotype observed in cystic fibrosis patients homozygous for the E831X mutation (2623G>T) in the CFTR gene. Analyses performed on nasal epithelial cell mRNA detected three distinct isoforms, a considerably more complex situation than expected for a single nucleotide substitution. Structure-function studies and in silico analyses provided the first experimental evidence of an indel of a stop codon by alternative splicing at a NAGNAG acceptor site. In addition to contributing to proteome plasticity, alternative splicing at a NAGNAG tandem site can thus remove a disease-causing UAG stop codon. This molecular study reveals a naturally occurring mechanism where the effect of either modifier genes or epigenetic factors could be suspected. This finding is of importance for genetic counseling as well as for deciding appropriate therapeutic strategies

A method for identifying alternative or cryptic donor splice sites within gene and mRNA sequences. Comparisons among sequences from vertebrates, echinoderms and other groups

<p>Abstract</p> <p>Background</p> <p>As the amount of genome sequencing data grows, so does the problem of computational gene identification, and in particular, the splicing signals that flank exon borders. Traditional methods for identifying splicing signals have been created and optimized using sequences from model organisms, mostly vertebrate and yeast species. However, as genome sequencing extends across the animal kingdom and includes various invertebrate species, the need for mechanisms to recognize splice signals in these organisms increases as well. With that aim in mind, we generated a model for identifying donor and acceptor splice sites that was optimized using sequences from the purple sea urchin, <it>Strongylocentrotus purpuratus</it>. This model was then used to assess the possibility of alternative or cryptic splicing within the highly variable immune response gene family known as <it>185/333</it>.</p> <p>Results</p> <p>A donor splice site model was generated from <it>S. purpuratus </it>sequences that incorporates non-adjacent dependences among positions within the 9 nt splice signal and uses position weight matrices to determine the probability that the site is used for splicing. The <it>Purpuratus </it>model was shown to predict splice signals better than a similar model created from vertebrate sequences. Although the <it>Purpuratus </it>model was able to correctly predict the true splice sites within the <it>185/333 </it>genes, no evidence for alternative or trans-gene splicing was observed.</p> <p>Conclusion</p> <p>The data presented herein describe the first published analyses of echinoderm splice sites and suggest that the previous methods of identifying splice signals that are based largely on vertebrate sequences may be insufficient. Furthermore, alternative or trans-gene splicing does not appear to be acting as a diversification mechanism in the <it>185/333 </it>gene family.</p