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At least 685 records · Page 38Linked to original sources
PubMed2005

Drosophila RNAi screen reveals CD36 family member required for mycobacterial infection.

Certain pathogens, such as Mycobacterium tuberculosis, survive within the hostile intracellular environment of a macrophage. To identify host factors required for mycobacterial entry and survival within macrophages, we performed a genomewide RNA interference screen in Drosophila macrophage-like cells, using Mycobacterium fortuitum. We identified factors required for general phagocytosis, as well as those needed specifically for mycobacterial infection. One specific factor, Peste (Pes), is a CD36 family member required for uptake of mycobacteria, but not Escherichia coli or Staphylococcus aureus. Moreover, mammalian class B scavenger receptors (SRs) conferred uptake of bacteria into nonphagocytic cells, with SR-BI and SR-BII uniquely mediating uptake of M. fortuitum, which suggests a conserved role for class B SRs in pattern recognition and innate immunity.

Animals↗
PubMed2005

Genome-wide RNAi screen for host factors required for intracellular bacterial infection.

Most studies of host-pathogen interactions have focused on pathogen-specific virulence determinants. Here, we report a genome-wide RNA interference screen to identify host factors required for intracellular bacterial pathogenesis. Using Drosophila cells and the cytosolic pathogen Listeria monocytogenes, we identified 305 double-stranded RNAs targeting a wide range of cellular functions that altered L. monocytogenes infection. Comparison to a similar screen with Mycobacterium fortuitum, a vacuolar pathogen, identified host factors that may play a general role in intracellular pathogenesis and factors that specifically affect access to the cytosol by L. monocytogenes.

Animals↗
PubMed2005

RNA-guided DNA deletion in Tetrahymena: an RNAi-based mechanism for programmed genome rearrangements.

Ciliated protozoan are unicellular eukaryotes. Most species in this diverse group display nuclear dualism, a special feature that supports both somatic and germline nuclei in the same cell. Probably due to this unique life style, they exhibit unusual nuclear characteristics that have intrigued researchers for decades. Among them are large-scale DNA rearrangements, which restructure the somatic genome to become drastically different from its germline origin. They resemble the classical phenomenon of chromatin diminution in some nematodes discovered more than a century ago. The mechanisms of such rearrangements, their biological roles, and their evolutionary origins have been difficult to understand. Recent studies have revealed a clear link to RNA interference, and begin to shed light on these issues. Using the simple ciliate Tetrahymena as a model, this chapter summarizes the physical characterization of these processes, describes recent findings that connect them to RNA interference, and discusses the details of their mechanisms, potential roles in genome defense, and possible occurrences in other organisms.

Animals↗
PubMed2006

Lentivector-mediated RNAi efficiently suppresses prion protein and prolongs survival of scrapie-infected mice.

Prion diseases are fatal neurodegenerative diseases characterized by the accumulation of PrP(Sc), the infectious and protease-resistant form of the cellular prion protein (PrP(C)). We generated lentivectors expressing PrP(C)-specific short hairpin RNAs (shRNAs) that efficiently silenced expression of the prion protein gene (Prnp) in primary neuronal cells. Treatment of scrapie-infected neuronal cells with these lentivectors resulted in an efficient and stable suppression of PrP(Sc) accumulation. After intracranial injection, lentiviral shRNA reduced PrP(C) expression in transgenic mice carrying multiple copies of Prnp. To test the therapeutic potential of lentiviral shRNA, we used what we believe to be a novel approach in which the clinical situation was mimicked. We generated chimeric mice derived from lentivector-transduced embryonic stem cells. Depending on the degree of chimerism, these animals carried the lentiviral shRNAs in a certain percentage of brain cells and expressed reduced levels of PrP(C). Importantly, in highly chimeric mice, survival after scrapie infection was significantly extended. Taken together, these data suggest that lentivector-mediated RNA interference could be an approach for the treatment of prion disease.

Animals↗
PubMed2004

RNAi-mediated silencing of CD40 prevents leukocyte adhesion on CD154-activated endothelial cells.

The CD40-CD154 dyad has a central role in the development of immune-inflammatory processes. Therefore, disruption of CD40 signaling has the potential to be therapeutically useful in a number of disease indications, including autoimmune syndromes, atherosclerosis, and allograft rejection. Blocking antibodies to CD154 have been successfully employed in experimental animal models, and recently in clinical trials, to prevent or treat these immunologically induced diseases. However, the thrombotic events observed in some of these studies raise important issues regarding future use of anti-CD154 antibodies in humans. In this study, we demonstrate that a small interfering RNA (siRNA) can effectively reduce the surface expression of the human CD40 costimulatory receptor. Moreover, by rendering endothelial cells unresponsive to CD154(+) Jurkat cell-mediated activation through RNA interference, induction of endothelial cell-adhesion molecule expression and leukocyte adhesion is prevented in vitro. Thus, anti-CD40 siRNA may become a safe and effective therapeutic option for interfering with CD40-CD154-mediated acute or chronic immune-inflammatory conditions.

Anti-Inflammatory Agents↗
PubMed2004

RNAi-induced down-regulation of FLT3 expression in AML cell lines increases sensitivity to MLN518.

FMS-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase that is constitutively activated in approximately 30% of acute myelogenous leukemia (AML) patients and appears to confer an adverse prognosis. Thus, development of inhibitors and/or antibodies that specifically target FLT3 has been of substantial interest. In this regard, phase 1 and 2 trials involving FLT3 inhibitors have recently reported FLT3 inhibition and leukemic blast reduction in some patients. Despite this, issues such as specificity and resistance need to be addressed. Consequently, the development of alternative approaches for targeting FLT3 would be of great consequence. In the present report, we demonstrate that FLT3 siRNA effectively down-regulates FLT3 expression in Ba/F3 cells transfected with FLT3 containing an activating internal tandem duplication (ITD) in the juxtamembrane domain and FLT3-ITD-positive Molm-14 human leukemia cells. Treatment with the FLT3 siRNA results in growth inhibition and apoptosis of these cells. Furthermore, siRNA-induced down-regulation of FLT3 increased the sensitivity of both cell lines to treatment with the FLT3 inhibitor MLN518. This illustrates the potential benefit of combined therapeutic approaches.

Cell Line, Tumor↗
PubMed2006

RNAi-mediated silencing of TEL/AML1 reveals a heat-shock protein- and survivin-dependent mechanism for survival.

The TEL/AML1 fusion gene results from the most frequent t(12;21)(p13;q22) translocation in childhood acute lymphoblastic leukemia (ALL). Its contribution to transformation is largely unknown, in particular with respect to survival and apoptosis. We therefore silenced TEL/AML1 expression in leukemic REH cells by RNA inhibition, which eventually led to programmed cell death. Microarray and 2D gel electrophoresis data demonstrated a differential regulation of heat-shock proteins (HSPs), among them HSP90, as well as of its client, survivin. Consistent with these findings, ectopic expression of TEL/AML1 in Ba/F3 cells increased protein levels of HSP90 and survivin and conferred resistance to apoptotic stimuli. Our data suggest that TEL/AML1 not only contributes to leukemogenesis by affecting an antiapoptotic network but also seems to be indispensable for maintaining the malignant phenotype. The functional relationship between TEL/AML1, HSP90, and survivin provides the rational for targeted therapy, be it the fusion gene or the latter 2 proteins.

Base Sequence↗
PubMed2006

RCAS-RNAi: a loss-of-function method for the developing chick retina.

BACKGROUND: The embryonic chick provides an excellent model system for studies of development. However, it has lacked an efficient loss-of-function method for studies of gene function. RESULTS: We show that avian retroviruses can deliver hairpins mediating RNA interference to the developing chick eye. These viruses 'knock down' specific genes in infected areas of the retina. The knock down persists as the retina matures and can be detected using in situ hybridization. Furthermore, the amount of retinal tissue affected can be controlled by manipulating the degree of infection. CONCLUSION: This technique provides a rapid and efficient loss-of-function option for studies in the developing chick retina.

Animals↗
PubMed2003

Knockdown of STAT3 expression by RNAi induces apoptosis in astrocytoma cells.

BACKGROUND: Astrocytomas are the most common type of primary central nervous system tumors. They are frequently associated with genetic mutations that deregulate cell cycle and render these tumors resistant to apoptosis. STAT3, signal transducer and activator of transcription 3, participates in several human cancers by inducing cell proliferation and inhibiting apoptosis and is frequently activated in astrocytomas. METHODS: RNA interference was used to knockdown STAT3 expression in human astrocytes and astrocytoma cell lines. The effect of STAT3 knockdown on apoptosis, cell proliferation, and gene expression was then assessed by standard methods. RESULTS: We have found that STAT3 is constitutively activated in several human astrocytoma cell lines. Knockdown of STAT3 expression by siRNA induces morphologic and biochemical changes consistent with apoptosis in several astrocytoma cell lines, but not in primary human astrocytes. Moreover, STAT3 is required for the expression of the antiapoptotic genes survivin and Bcl-xL in the A172 glioblastoma cell line. CONCLUSION: These results show that STAT3 is required for the survival of some astrocytomas. These studies suggest STAT3 siRNA could be a useful therapeutic agent for the treatment of astrocytomas.

Apoptosis↗
PubMed2006

RNAi dependent epigenetic marks on a geminivirus promoter.

Nicotiana benthamiana plants were stably transformed with an intron-spliced dsRNA producing construct cognate to bidirectional promoter of African cassava mosaic geminivirus (ACMV) DNA A. Transgenic lines expressed multiple siRNAs species upon ACMV infection. The de novo DNA methylation and an increased proportion of histone H3 Lysine-9 methylation (H3K9) at intergenic region (IGR) of ACMV DNA A were observed.

DNA Methylation↗
PubMed2002

RNAi hushes heterochromatin.

Repeated DNA elements and region-specific protein modifications combine within chromosomes to form a transcriptionally silent chromatin structure called heterochromatin. Recent work in the fission yeast Schizosaccharomyces pombe reveals that RNA is also an integral component of silent heterochromatin, providing a new perspective on how heterochromatin is organized and maintained in eukaryotic cells.

Animals↗