SEARCH · PubMed Health

Results for “TLS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed1998

The transcription factor Spi-1/PU.1 interacts with the potential splicing factor TLS.

Spi-1/PU.1 is an Ets protein deregulated by insertional mutagenesis during the murine Friend erythroleukemia. The overexpression of the normal protein in a proerythroblastic cell prevents its terminal differentiation. In normal hematopoiesis Spi-1/PU.1 is a transcription factor that plays a key role in normal myeloid and B lymphoid differentiation. Moreover, Spi-1/PU.1 binds RNA and interferes in vitro with the splicing process. Here we report that Spi-1 interacts in vivo with TLS (translocated in liposarcoma), a RNA-binding protein involved in human tumor-specific chromosomal translocations. This interaction appears functionally relevant, since TLS is capable of reducing the abilities of Spi-1/PU.1 to bind DNA and to transactivate the expression of a reporter gene. In addition, we observe that TLS is potentially a splicing factor. It promotes the use of the distal 5' splice site during the E1A pre-mRNA splicing. This effect is counterpoised in vivo by Spi-1. These data suggest that alteration of pre-mRNA alternative splicing by Spi-1 could be involved in the transformation of an erythroblastic cell.

Alternative Splicing↗

PubMed1989

Segmented anisotropic refinement of bovine ribonuclease A by the application of the rigid-body TLS model.

The anisotropic displacements of selected rigid groups in bovine ribonuclease A have been refined from X-ray diffraction data by the application of the rigid-body TLS model. The rigid groups chosen were the side chains of tyrosine, histidine and phenylalanine and the planar side chains of aspartic acid, glutamic acid, glutamine, asparagine and arginine. The method has also been applied to the co-crystallizing active-site sulfate anion. This has enabled the description of the motion of the above-mentioned side-chain atoms by anisotropic displacement ellipsoids from a 1.45 A refinement. The hydrophobic side groups in the protein core show mainly translational motion, with mean-square librations of 20 deg2 which are similar to those found in some close-packed crystals of small organic molecules. Librational displacements are much more significant in the hydrophilic side groups where their magnitudes can be correlated with solvent accessibility. Large librations of some solvent exposed side chains correspond with the breakdown of a simple TLS model and the existence of multiple orientations of the side groups. The TLS model has also been applied to the whole protein molecule and shows that the average motion is approximately isotropic with little librational character.

Animals↗

PubMed1999

Identification of genes differentially expressed in TLS-CHOP carrying myxoid liposarcomas.

Myxoid liposarcomas (MLS) carry a t(12;16) or, more rarely, a t(12;22) resulting in fusion of the transcription factor gene CHOP on chromosome 12 with TLS/FUS on chromosome 16 or EWS on chromosome 22. The chimeric TLS-CHOP or EWS-CHOP proteins most probably function as abnormal transcription factors, causing transcriptional de-regulation of several target genes and relaxation of functions critical for growth and differentiation control. A PCR-based subtractive hybridization technique was used to identify genes that are differentially expressed in TLS-CHOP-carrying MLS but not in normal fat tissue. Six myxoid-liposarcoma-associated transcripts, MLAT, were isolated. The genes identified as MLAT can be divided into 2 groups. MLAT1, 2 and 6 show high similarity to glia-derived nexin, neuronatin and the RET oncogene, respectively, all normally involved in development of tissues of neural origin. MLAT3 to MLAT5 represent new genes.

CCAAT-Enhancer-Binding Proteins↗

PubMed2001

The TolC protein of Escherichia coli serves as a cell-surface receptor for the newly characterized TLS bacteriophage.

The TolC protein of Escherichia coli is implicated in a variety of diverse cellular functions, including antibiotic efflux and alpha-hemolysin secretion. An incidental role of TolC is to facilitate the entry of the bacteriophage TLS and colicin E1 into the bacterial cell. Despite the resolution of TolC's atomic structure, the roles of specific residues in its diverse functions are unknown. Here, we describe a genetic strategy for isolating missense tolC mutations that abolish the bacteriophage receptor activity of the TolC protein without influencing its role in antibiotic efflux. These spontaneous mutations affected two regions of the TolC protein and included base-pair substitutions, insertions, and deletions. Comparison of the TolC sequence with those of its homologues revealed two hypervariable stretches that were predicted to represent loops. Interestingly, all but one of the TolC alterations preventing phage binding were located in these two hypervariable regions, which are likely to be exposed on the cell surface. This was substantiated by the recently solved three-dimensional structure of TolC. Curiously, all the phage-resistant TolC mutants showed varying degrees of resistance to colicin E1, suggesting the involvement of overlapping regions of TolC in colicin E1 import and phage binding. The phage used in this study, TLS, was earlier reported as a strain of U3. However, we show here that, unlike the previously reported lipopolysaccharide-specific U3 phage, this phage displays a distinctly different host range and discrete morphological features and, in addition to utilizing TolC as receptor, it requires the inner core of a lipopolysaccharide.

Adsorption↗

PubMed1999

Characteristics of genomic breakpoints in TLS-CHOP translocations in liposarcomas suggest the involvement of Translin and topoisomerase II in the process of translocation.

Fusion of TLS/FUS and CHOP gene by reciprocal translocation t(12;16)(q32;q16) is a common genetic event found in myxoid and round-cell liposarcomas. Characterization of this genetic event was performed by three methods, Southern blot, RT-PCR, and genomic long-distance PCR in nine myxoid and three round-cell liposarcomas. All but one tumors showed genetic alternations indicating the fusion of TLS/FUS and CHOP gene. Two novel types of fusion transcripts were found, of which one lacked exon 2 sequence of CHOP gene, and the other lacked 3' half of exon 5 of TLS gene. The latter case was caused by a cryptic splicing site which was created by the genomic fusion. Detailed analyses genomic fusion points revealed several sequence characteristics surrounding the fusion points. Homology analyses of breakpoint sequences with known sequence motifs possibly involve in the process of translocation uncovered Translin binding sequences at both of TLS/ FUS and CHOP breakpoints in two cases. Translocations were always associated with other genetic alterations, such as deletions, duplications, or insertions. Short direct repeats were almost always found at both ends of deleted or duplicated fragments some of which had apparently been created by joining of sequences that flank the rearrangement. Finally, consensus topoisomerase II cleavage sites were found at breakpoints in all cases analysed, suggesting a role of this enzyme in creating staggered ends at the breakpoint. These data suggested that sequence characteristics may play an important role to recruit several factors such as Translin and topoisomerase II in the process of chromosomal translation in liposarcomas.

Artificial Gene Fusion↗

PubMed2002

TLS-CHOP target gene DOL54 expression in liposarcomas and malignant fibrous histiocytomas.

Downstream of the gene for the liposarcoma-associated fusion oncoprotein 54 (DOL54) is a target gene of the myxoid liposarcoma and round cell liposarcoma (M-LPS/RC-LPS) oncogene, TLS/FUS-CHOP. The DOL54 gene product is closely associated with adipogenic differentiation. DOL54 overexpression resulted in tumorigenicity when Chinese Hamster Ovary (CHO) cells were injected subcutaneously into nude mice. The biological significance of DOL54 expression for human malignant soft tissue tumors, however, has not yet been investigated. We examined TLS-CHOP and DOL54 expression in M-LPS/RC-LPS, well-differentiated liposarcoma and malignant fibrous histiocytoma (MFH), a tumor whose cellular origin has not been determined. We observed DOL54 expression in 50% of M-LPS/RC-LPS cases (in which TLS-CHOP was also expressed) and 33% of MFH cases, suggesting that a portion of MFH lesions may either derive from adipocytic precursor cells or have the potential to undergo adipogenic differentiation. In this manner, M-LPS/RC-LPS and MFH lesions may share tumorigenic characteristics, resulting from the unscheduled expression of DOL54.

Blotting, Northern↗

PubMed1998

Retroviral transduction of TLS-ERG initiates a leukemogenic program in normal human hematopoietic cells.

Many chimeric oncogenes have been identified by virtue of the association between chromosomal translocation and specific human leukemias. However, the biological mechanism by which these oncogenes disrupt the developmental program of normal human hematopoietic cells during the initiation of the leukemogenic process is poorly understood due to the absence of an appropriate experimental system to study their function. Here, we report that retroviral transduction of TLS-ERG, a myeloid leukemia-associated fusion gene, to human cord blood cells results in altered myeloid and arrested erythroid differentiation and a dramatic increase in the proliferative and self-renewal capacity of transduced myeloid progenitors. Thus, TLS-ERG expression alone induced a leukemogenic program that exhibited similarities to the human disease associated with this translocation. These results provide an experimental examination of the early stages of the human leukemogenic process induced by a single oncogene and establish a paradigm to functionally assay putative leukemogenic genes in normal human hematopoietic cells.

Cell Lineage↗

PubMed1995

Cabeza, a Drosophila gene encoding a novel RNA binding protein, shares homology with EWS and TLS, two genes involved in human sarcoma formation.

We have previously described a partial Drosophila cDNA, clone P19, which bears homology to members of the RNA recognition motif (RRM) family of proteins [Haynes et al. (1987) Proc. Natl. Acad. Sci. USA, 84, 1819-1823]. RNA binding as well as involvement in RNA processing has been demonstrated for some RRM proteins. We report here the further characterization of P19, which we renamed cabeza (caz). caz is located on the X chromosome at position 14B. Using Northern analysis, at least four transcripts from the caz gene were observed at varying levels during development. caz mRNA and protein are enriched in the brain and central nervous system during embryogenesis. In addition, the protein is enriched in the adult head. UV crosslinking was used to demonstrate in vitro RNA binding activity for full-length recombinant caz protein and for the caz RRM domain. Sequence analysis revealed caz is related to two human genes, EWS and TLS, which are involved in chromosomal translocations. The fusion of EWS and TLS to other cellular genes results in sarcoma formation. In addition to their overall structural organization and sequence similarity, these three genes share an RRM which is divergent from typical RRMs. Therefore, it appears that these genes constitute a new sub-family of RNA binding proteins.

Amino Acid Sequence↗

PubMed1994

CHOP (GADD153) and its oncogenic variant, TLS-CHOP, have opposing effects on the induction of G1/S arrest.

The growth arrest and DNA damage-inducible gene CHOP (GADD153) encodes a small nuclear protein from the C/EBP family, originally isolated from adipocytes in culture. Although inactive in cells under normal conditions, the CHOP gene is markedly induced by a variety of cellular stresses, including nutrient deprivation and metabolic perturbations. These lead to accumulation of CHOP protein in the nucleus. Because cellular stress normally leads to growth arrest, we examined the implication of CHOP in this process. Microinjection of CHOP expression plasmids into NIH-3T3 cells blocked the cells from progressing through the cell cycle, measured by an attenuation in the fraction of cells incorporating BrdU, an S-phase marker. The precise point in the cell cycle at which CHOP acts was mapped by microinjection of bacterially expressed CHOP protein into synchronized cells--this blocked the cells from progressing from G1 to S phase. This effect of CHOP was observed only when the protein was introduced early after serum stimulation suggesting that CHOP works at or around the so-called G1/S checkpoint. CHOP dimerizes with other C/EBP proteins and the CHOP-C/EBP dimers are directed away from "classical" C/EBP sites recognizing instead unique "nonclassical" sites. Mutant forms of the CHOP protein that lack the leucine zipper dimerization domain or the unusually structured basic region, potentially involved in DNA binding, fail to induce growth arrest. A tumor-specific form of CHOP, TLS-CHOP, that has been found so far exclusively in the human adipose tissue tumor myxoid liposarcoma, fails to cause growth arrest and furthermore interferes with the ability of normal CHOP to induce growth arrest. CHOP has been shown recently to be markedly inducible by nutritional deprivation of cells. This suggests that CHOP may play a role in an inducible growth arrest pathway that is triggered by metabolic cues and is of particular importance in adipose tissue--an organ that undergoes marked changes in its metabolic activity. Blocking of this pathway by TLS-CHOP may play a mechanistic role in the establishment of myxoid liposarcoma.

3T3 Cells↗

PubMed2006

Optimal description of a protein structure in terms of multiple groups undergoing TLS motion.

A single protein crystal structure contains information about dynamic properties of the protein as well as providing a static view of one three-dimensional conformation. This additional information is to be found in the distribution of observed electron density about the mean position of each atom. It is general practice to account for this by refining a separate atomic displacement parameter (ADP) for each atomic center. However, these same displacements are often described well by simpler models based on TLS (translation/libration/screw) rigid-body motion of large groups of atoms, for example interdomain hinge motion. A procedure, TLSMD, has been developed that analyzes the distribution of ADPs in a previously refined protein crystal structure in order to generate optimal multi-group TLS descriptions of the constituent protein chains. TLSMD is applicable to crystal structures at any resolution. The models generated by TLSMD analysis can significantly improve the standard crystallographic residuals R and R(free) and can reveal intrinsic dynamic properties of the protein.

Algorithms↗

PubMed1993

Molecular dynamics simulations and rigid body (TLS) analysis of aspartate carbamoyltransferase: evidence for an uncoupled R state.

In the R form of ATCase complexed with the bisubstrate analogue, N-(phosphonacetyl)-L-aspartate, large temperature factors are reported for the allosteric domains of the regulatory chains. We studied the conformational flexibility of the holoenzyme with molecular dynamics simulations and rigid body (TLS) analysis. The results of the molecular dynamics simulations suggest that, although local atomic fluctuations account for the temperature factors of the catalytic and zinc domains, they do not account for the large temperature factors of the allosteric regions. However, the temperature factors of the allosteric domains can be satisfactorily analyzed using a rigid body model. The simulations and rigid body analysis support the idea that the allosteric regions are mechanically uncoupled from the rest of the enzyme in the PALA structure. Implications of this uncoupling for allosteric regulation are discussed.

Allosteric Site↗

PubMed1996

Molecular cloning and subcellular localisation of the snRNP-associated protein 69KD, a structural homologue of the proto-oncoproteins TLS and EWS with RNA and DNA-binding properties.

We recently isolated and characterised a 69 kDa protein (69KD) found associated with spliceosomal small nuclear ribonucleoproteins (snRNPs). Here, we report the molecular cloning of a cDNA encoding this protein, its nucleic acid binding properties and its subcellular localisation. Sequence analysis of the 69KD cDNA revealed: (1) that 69KD shares structural similarity with the human RNA binding proteins TLS and EWS (95% and 65% identity, respectively), the products of two genes frequently targeted by tumour-specific chromosomal translocations; (2) that 69KD contains a consensus RNA binding domain (CS-RBD) and three Arg/Gly-rich RNA binding motifs, structural features typical of many RNA binding proteins, in particular of hnRNP proteins; and (3) that 69KD contains a single putative Cys2/Cys2 zinc finger domain, a characteristic of many DNA-binding proteins. Consistent with its possession of these motifs, 69KD display a general nucleic acid binding activity, with a strong preference for guanyl and uridyl-rich RNA sequences, as well as for single-stranded and double-stranded DNA. The functional significance of this affinity for nucleic acids remains unclear. However, based on the established association of 69KD with the Sm core domain of snRNPs in vivo, these motifs might help mediate 69KD binding to snRNPs or be involved in some, as yet, unknown aspect of RNA metabolism. Consistent with both possibilities, 69KD is detected within typical snRNP containing subnuclear structures referred to as speckles, and is also more widely distributed throughout the nucleoplasm, as observed for many hnRNP proteins.

Amino Acid Sequence↗

PubMed2001

High molecular weight lipids from the trilaminar outer wall (TLS)-containing microalgae Chlorella emersonii, Scenedesmus conmmunis and Tetraedron minimum.

High molecular weight lipids were isolated from Chlorella emersonii, Scenedesmus communis and Tetraedron minimum, thin trilaminar outer wall (TLS)-containing freshwater microalgae producing an insoluble non-hydrolysable biopolymer (i.e. algaenan). Molecular weight determination by gel permeation chromatography indicated that their molecular weights range from ca. 400 to 2000 Da. Flash pyrolysis with in situ methylation using tetramethylammonium hydroxide (TMAH) and alkaline hydrolysis showed that the high molecular weight lipids isolated from C. emersonii and S. communis are mainly composed of saturated n-C26 and n-C28 fatty acids and alcohols and of saturated n-C30 and n-C32 alpha,omega-diols and omega-hydroxy acids. In contrast the high molecular weight lipids isolated from T. minimum are predominantly composed of long-chain fatty acids and omega-hydroxy acids. Aromatic moieties were also identified in small amounts in the thermochemolysate and in the hydrolysate. Chemical structural models containing long-chain mono- and polyesters were proposed for the high molecular weight lipids isolated from the three microalgae in agreement with analytical and spectroscopic data. Structural similarity between the outer cell wall of these microalgae and the cuticular membrane of higher plants is suggested.

Cell Wall↗

PubMed1999

Ultrasensitive determination of beta-carotene in fish oil-based supplementary drugs by HPLC-TLS.

This research study demonstrates that thermal lens spectrometry (TLS) combined with efficient isocratic HPLC separation provides an excellent analytical means to profile and quantify carotenes in fish body oils and possibly also in vegetable oils. In particular, a highly sensitive, selective, simple and rapid method for the determination of ultratraces of beta-carotene in fish oil-based supplementary drugs has been proposed. The analyte could be determined reliably and precisely in the presence of a complex matrix including other fat-soluble vitamins (A, D and E), polyunsaturated fatty acids, sterols and other pigments by matrix-matched calibration in cod liver oil. The suitability of the method is also evidenced by favourable analytical figures of merit for beta-carotene such as a linearity range of 1-120 ng ml(-1), LOD of 0.58 ng ml(-1), recovery of 101.4+/-3.3% and measurement repeatability of 4.1%.

Antioxidants↗

PubMed2004

A single amino acid change (E85K) in human PCNA that leads, relative to wild type, to enhanced DNA synthesis by DNA polymerase delta past nucleotide base lesions (TLS) as well as on unmodified templates.

Human proliferating cell nuclear antigen (hPCNA) containing a single amino acid substitution at position 85, that of lysine for glutamate (E85K), was compared to wild-type (wt) hPCNA for its ability to promote DNA synthesis by purified DNA polymerase delta (pol delta) both on unmodified templates and past chemically defined template base lesions (translesion synthesis; TLS). Significant enhancement (up to 4-5-fold or greater) was seen but depended both on the exact PCNA/pol delta ratio tested and on the specific nature of the template (e.g., unmodified versus lesion-containing; chemical nature of the template base lesion). These results suggest that human PCNA, either mutated to contain lysine (K) at position 85 or bearing similar primary mutations, would promote more secondary mutagenesis in cells and/or tissues where PCNA is normally expressed at low levels relative to pol delta. Over an entire lifetime, such secondary mutagenesis could be biomedically significant.

Amino Acid Substitution↗

PubMed2002

The complete genome sequence of Chlorobium tepidum TLS, a photosynthetic, anaerobic, green-sulfur bacterium.

The complete genome of the green-sulfur eubacterium Chlorobium tepidum TLS was determined to be a single circular chromosome of 2,154,946 bp. This represents the first genome sequence from the phylum Chlorobia, whose members perform anoxygenic photosynthesis by the reductive tricarboxylic acid cycle. Genome comparisons have identified genes in C. tepidum that are highly conserved among photosynthetic species. Many of these have no assigned function and may play novel roles in photosynthesis or photobiology. Phylogenomic analysis reveals likely duplications of genes involved in biosynthetic pathways for photosynthesis and the metabolism of sulfur and nitrogen as well as strong similarities between metabolic processes in C. tepidum and many Archaeal species.

Carbon Dioxide↗

PubMed1992

The segmented anisotropic refinement of monoclinic papain by the application of the rigid-body TLS model and comparison to bovine ribonuclease A.

The anisotropic displacements of selected rigid groups in monoclinic papain have been refined from X-ray diffraction data by application of the rigid-body TLS model. The rigid groups chosen were the aromatic side chains of tryptophan, tyrosine, histidine and phenylalanine, and the planar carboxylic and guanidinium side chains of aspartic acid, glutamic acid, glutamine, asparagine and arginine. The derived translation and libration tensors have been compared with those previously derived for bovine ribonuclease A and provide evidence for different modes and anisotropies of displacement over the two proteins.

Amino Acids↗

PubMed2000

BCR-ABL prevents c-jun-mediated and proteasome-dependent FUS (TLS) proteolysis through a protein kinase CbetaII-dependent pathway.

The DNA binding activity of FUS (also known as TLS), a nuclear pro-oncogene involved in multiple translocations, is regulated by BCR-ABL in a protein kinase CbetaII (PKCbetaII)-dependent manner. We show here that in normal myeloid progenitor cells FUS, although not visibly ubiquitinated, undergoes proteasome-dependent degradation, whereas in BCR-ABL-expressing cells, degradation is suppressed by PKCbetaII phosphorylation. Replacement of serine 256 with the phosphomimetic aspartic acid prevents proteasome-dependent proteolysis of FUS, while the serine-256-to-alanine FUS mutant is unstable and susceptible to degradation. Ectopic expression of the phosphomimetic S256D FUS mutant in granulocyte colony-stimulating factor-treated 32Dcl3 cells induces massive apoptosis and inhibits the differentiation of the cells escaping cell death, while the degradation-prone S256A mutant has no effect on either survival or differentiation. FUS proteolysis is induced by c-Jun, is suppressed by BCR-ABL or Jun kinase 1, and does not depend on c-Jun transactivation potential, ubiquitination, or its interaction with Jun kinase 1. In addition, c-Jun-induced FUS proteasome-dependent degradation is enhanced by heterogeneous nuclear ribonucleoprotein (hnRNP) A1 and depends on the formation of a FUS-Jun-hnRNP A1-containing complex and on lack of PKCbetaII phosphorylation at serine 256 but not on FUS ubiquitination. Thus, novel mechanisms appear to be involved in the degradation of FUS in normal myeloid cells; moreover, the ability of the BCR-ABL oncoprotein to suppress FUS degradation by the induction of posttranslational modifications might contribute to the phenotype of BCR-ABL-expressing hematopoietic cells.

Animals↗