Re-localization of Cellular Protein SRp20 during Poliovirus Infection: Bridging a Viral IRES to the Host Cell Translation Apparatus

Poliovirus IRES-mediated translation requires the functions of certain canonical as well as non-canonical factors for the recruitment of ribosomes to the viral RNA. The interaction of cellular proteins PCBP2 and SRp20 in extracts from poliovirus-infected cells has been previously described, and these two proteins were shown to function synergistically in viral translation. To further define the mechanism of ribosome recruitment for the initiation of poliovirus IRES-dependent translation, we focused on the role of the interaction between cellular proteins PCBP2 and SRp20. Work described here demonstrates that SRp20 dramatically re-localizes from the nucleus to the cytoplasm of poliovirus-infected neuroblastoma cells during the course of infection. Importantly, SRp20 partially co-localizes with PCBP2 in the cytoplasm of infected cells, corroborating our previous in vitro interaction data. In addition, the data presented implicate the presence of these two proteins in viral translation initiation complexes. We show that in extracts from poliovirus-infected cells, SRp20 is associated with PCBP2 bound to poliovirus RNA, indicating that this interaction occurs on the viral RNA. Finally, we generated a mutated version of SRp20 lacking the RNA recognition motif (SRp20ΔRRM) and found that this protein is localized similar to the full length SRp20, and also partially co-localizes with PCBP2 during poliovirus infection. Expression of this mutated version of SRp20 results in a ∼100 fold decrease in virus yield for poliovirus when compared to expression of wild type SRp20, possibly via a dominant negative effect. Taken together, these results are consistent with a model in which SRp20 interacts with PCBP2 bound to the viral RNA, and this interaction functions to recruit ribosomes to the viral RNA in a direct or indirect manner, with the participation of additional protein-protein or protein-RNA interactions

Editing of hnRNP K protein mRNA in colorectal adenocarcinoma and surrounding mucosa

The heterogeneous nuclear ribonucleoprotein K (hnRNP K) protein is an RNA-binding protein involved in many processes that compose gene expression. K protein is upregulated in the malignant processes and has been shown to modulate the expression of genes involved in mitogenic responses and tumorigenesis. To explore the possibility that there are alternative isoforms of K protein expressed in colon cancer, we amplified and sequenced K protein mRNA that was isolated from colorectal cancers as well as from normal tissues surrounding the tumours. Sequencing revealed a single G-to-A base substitution at position 274 that was found in tumours and surrounding mucosa, but not in individuals that had no colorectal tumour. This substitution most likely reflects an RNA editing event because it was not found in the corresponding genomic DNAs. Sequencing of RNA from normal colonic mucosa of patients with prior resection of colorectal cancer revealed only the wild-type K protein transcript, indicating that G274A isoform is tumour related. To our knowledge, this is the first example of an RNA editing event in cancer and its surrounding tissue, a finding that may offer a new diagnostic and treatment marker

Measurement of lentiviral vector titre and copy number by cross-species duplex quantitative PCR

Lentiviruses are the vectors of choice for many preclinical studies and clinical applications of gene therapy. Accurate measurement of biological vector titre before treatment is a prerequisite for vector dosing, and the calculation of vector integration sites per cell after treatment is as critical to the characterisation of modified cell products as it is to long-term follow-up and the assessment of risk and therapeutic efficiency in patients. These analyses are typically based on quantitative real-time PCR (qPCR), but as yet compromise accuracy and comparability between laboratories and experimental systems, the former by using separate simplex reactions for the detection of endogene and lentiviral sequences and the latter by designing different PCR assays for analyses in human cells and animal disease models. In this study, we validate in human and murine cells a qPCR system for the single-tube assessment of lentiviral vector copy numbers that is suitable for analyses in at least 33 different mammalian species, including human and other primates, mouse, pig, cat and domestic ruminants. The established assay combines the accuracy of single-tube quantitation by duplex qPCR with the convenience of one-off assay optimisation for cross-species analyses and with the direct comparability of lentiviral transduction efficiencies in different species

Williams-Beuren syndrome TRIM50 encodes an E3 ubiquitin ligase.

Williams-Beuren syndrome (WBS) is a neurodevelopmental and multisystemic disease that results from hemizygosity of approximately 25 genes mapping to chromosomal region 7q11.23. We report here the preliminary description of eight novel genes mapping within the WBS critical region and/or its syntenic mouse region. Three of these genes, TRIM50, TRIM73 and TRIM74, belong to the TRIpartite motif gene family, members of which were shown to be associated to several human genetic diseases. We describe the preliminary functional characterization of these genes and show that Trim50 encodes an E3 ubiquitin ligase, opening the interesting hypothesis that the ubiquitin-mediated proteasome pathway might be involved in the WBS phenotype