New alternative splicing variants of the ATXN2 transcript.

Background: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant disorder with progressive degeneration of cerebellar Purkinje cells and selective loss of neurons in the brainstem. This neurodegenerative disorder is caused by the expansion of a polyglutamine domain in ataxin-2. Ataxin-2 is composed of 1312 amino acids, has a predicted molecular weight of 150-kDa and is widely expressed in neuronal and non-neuronal tissues.

Ataxin-2 modulates the levels of Grb2 and SRC but not ras signaling.

Ataxin-2 (ATXN2) is implicated mainly in mRNA processing. Some ATXN2 associates with receptor tyrosine kinases (RTK), inhibiting their endocytic internalization through interaction of proline-rich domains (PRD) in ATXN2 with SH3 motifs in Src. Gain of function of ATXN2 leads to neuronal atrophy in the diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS).

ATXN2-CAG42 sequesters PABPC1 into insolubility and induces FBXW8 in cerebellum of old ataxic knock-in mice.

Spinocerebellar Ataxia Type 2 (SCA2) is caused by expansion of a polyglutamine encoding triplet repeat in the human ATXN2 gene beyond (CAG)(31). This is thought to mediate toxic gain-of-function by protein aggregation and to affect RNA processing, resulting in degenerative processes affecting preferentially cerebellar neurons. As a faithful animal model, we generated a knock-in mouse replacing the single CAG of murine Atxn2 with CAG42, a frequent patient genotype.

Ataxin-2 associates with rough endoplasmic reticulum.

Ataxin-2 is a novel protein, normally with a domain of 22 consecutive glutamine (Q) residues, which may expand beyond a threshold of (Q)(32), causing a neurodegenerative disease named Spinocerebellar ataxia type 2 (SCA2). To obtain clues about the functions of ataxin-2, we used fluorescence microscopy and centrifugation fractionation analyses. Immunocytochemical detection in non-neuronal and neuronal cells showed endogenous and transfected ataxin-2 distributed throughout the cytoplasm, with perinuclear preference and a granular appearance.

Ataxin-2 associates with the endocytosis complex and affects EGF receptor trafficking.

Ataxin-2 is a novel protein, where the unstable expansion of an internal polyglutamine domain can cause the neurodegenerative disease Spinocerebellar Ataxia type 2 (SCA2). To elucidate its cellular function, we have used full-length ataxin-2 as bait in a yeast two-hybrid screen of human adult brain cDNA. As binding partners we found endophilin A1 and A3, two brain-expressed members of the endophilin A family involved in synaptic vesicle endocytosis.

Insulin receptor and lipid metabolism pathology in ataxin-2 knock-out mice.

Ataxin-2 is a cytoplasmic protein, product of the SCA2 gene. Expansion of the normal polyglutamine tract in the protein leads to the neurodegenerative disorder Spino-Cerebellar Ataxia type 2 (SCA2). Although ataxin-2 has been related to polyribosomes, endocytosis and actin-cytoskeleton organization, its biological function remains unknown.

Ataxin-2 promotes apoptosis of human neuroblastoma cells.

Neuroblastoma is a highly heterogeneous tumor of young children. Although many advances have been made towards understanding the molecular mechanisms dictating the phenotypic heterogeneity, the prognosis of children with neuroblastoma, particularly of progressively growing variants, has remained dire. About 10% of neuroblastomas regress spontaneously, probably by apoptosis, while another 20% have amplified the MYCN gene resulting in a poor prognosis.

Selectable retrovirus vectors encoding Friend virus gp55 or erythropoietin induce polycythemia with different phenotypic expression and disease progression.

The Friend spleen focus-forming virus induces a massive expansion of erythroid progenitor cells resulting in polycythemia and splenomegaly. The pathogenic agent is the membrane glycoprotein gp55, encoded by the env gene. Recent evidence indicates that gp55 binds to and activates the erythropoietin (Epo) receptor.

Cooperation of GATA-1 and Sp1 can result in synergistic transcriptional activation or interference.

GATA-1 is a lineage-restricted transcription factor. Virtually all erythroid-expressed genes contain GATA recognition sites in their regulatory elements. Cotransfection/transactivation assays have revealed that, although GATA-1 as the only cell-restricted transcription factor is sufficient to activate some of the erythroid-specific promoters, not all such promoters are responsive, suggesting a requirement for cooperation with other factors.

The gene for erythropoietin receptor is expressed in multipotential hematopoietic and embryonal stem cells: evidence for differentiation stage-specific regulation.

The principal regulator of erythropoiesis is the glycoprotein erythropoietin, which interacts with a specific cell surface receptor (EpoR). A study aimed at analyzing EpoR gene regulation has shown that both pluripotent embryonal stem cells and early multipotent hematopoietic cells express EpoR transcripts. Commitment to nonerythroid lineages (e.

A single point mutation activates the Moloney murine leukemia virus long terminal repeat in embryonal stem cells.

The expression of Moloney murine leukemia virus (Mo-MuLV) and Mo-MuLV-derived vectors is restricted in undifferentiated mouse embryonal carcinoma and embryonal stem (ES) cells. We have previously described the isolation of retroviral mutants with host range properties expanded to embryonal cell lines. One of these mutants, the murine embryonic stem cell virus (MESV), is expressed in ES cell lines.

The T----C substitution at -198 of the A gamma-globin gene associated with the British form of HPFH generates overlapping recognition sites for two DNA-binding proteins.

Defects in the developmental changes of human hemoglobin production characterized by the continued expression of fetal globin during adult life are classified as hereditary persistence of fetal hemoglobin (HPFH). Among the various molecular lesions associated with this phenotype, the non-deletion forms with point mutations in the promoter region are thought to provide mechanistic clues for gamma-globin gene regulation. The natural occurrence of four different base substitutions mapping within six nucleotides of a homopurine.

The malignant histiocytosis sarcoma virus, a recombinant of Harvey murine sarcoma virus and Friend mink cell focus-forming virus, has acquired myeloid transformation specificity by alterations in the long terminal repeat.

The malignant histiocytosis sarcoma virus (MHSV), in contrast to other viruses with the ras oncogene, induces acute histiocytosis in newborn and adult mice. Molecular structure and function studies were initiated to determine the basis of its unique macrophage-transforming potential. Characterization of the genomic structure showed that the virus evolved by recombination of the Harvey murine sarcoma virus (Ha-MuSV) and a virus of the Friend-mink cell focus-forming virus family.

Interaction of the TGGCA-binding protein with upstream sequences is required for efficient transcription of mouse mammary tumor virus.

A high-affinity binding site for the TGGCA-binding protein, also known as nuclear factor I, has previously been shown to reside within the mouse mammary tumor virus (MMTV) long terminal repeat. We have introduced mutations into this binding site to test the importance of this ubiquitous nuclear protein in MMTV transcription. Mutations which abolish the binding of the TGGCA protein in vitro are shown to impair strongly glucocorticoid-induced transcription from this promoter in vivo.

DNase I-hypersensitive sites in the chromatin structure of the lysozyme gene in steroid hormone target and non-target cells.

The pattern of DNase I-hypersensitive sites in the chromatin domain of the lysozyme gene was investigated in several organs and cell-types of the chicken. In the cluster of hypersensitive chromatin sites framing the gene, different classes of sites could be discerned: A subset was common to essentially all cells examined except for erythrocytes. Thus several highly nuclease susceptible structures exist around the gene even in its repressed state.

Functional homology between the sequence-specific DNA-binding proteins nuclear factor I from HeLa cells and the TGGCA protein from chicken liver.

Nuclear factor I from HeLa cells, a protein with enhancing function in adenovirus DNA replication, and the chicken TGGCA protein are specific DNA-binding proteins that were first detected by independent methods and that appeared to have similar DNA sequence specificity. To test whether they are homologous proteins from different species we have compared (i) their DNA binding properties and (ii) their function in reconstituted adenovirus DNA replication systems. Using deletion and substitution mutants derived from the DNA binding site on the adenovirus 2 inverted terminal repeat, it was found that the two proteins protect the same 24-nucleotide region of both strands against DNase I digestion and that they have identical minimal recognition sequences of 15 bp containing dyad symmetry.

The TGGCA protein binds to the MMTV-LTR, the adenovirus origin of replication, and the BK virus enhancer.

TGGCA-binding proteins are nuclear proteins with high affinity for double-stranded DNA homologous to the prototype recognition sequence 5'YTGGCANNNTGCCAR 3'. Their ubiquitous tissue distribution in higher vertebrates characterizes them as a class of highly conserved proteins which may exert a basic function. To obtain clues to this function, specific binding sites were mapped on three viral genomes.

Alternative sets of DNase I-hypersensitive sites characterize the various functional states of the chicken lysozyme gene.

The structural organization of chromatin is thought to determine the state of differentiation and activity of eukaryotic genes. Local interruptions of the regular nucleosomal array, the so-called DNase-hypersensitive sites, may indicate regions of the genome which play a critical part in regulation of differential gene activity. We present here two new observations on the chromatin structure of the chicken lysozyme gene, which strongly support a regulatory function for these sites.

The TGGCA-binding protein: a eukaryotic nuclear protein recognizing a symmetrical sequence on double-stranded linear DNA.

Low salt extracts of chicken oviduct nuclei contain a DNA binding protein with high affinity for specific DNA sequences in the flanking regions of the chicken lysozyme gene. Two of the three binding sites found within a total of 11 kb upstream from the promoter are located only 92 bp apart from each other. Upon comparison of the DNA binding sites, the symmetrical consensus sequence 5'- TGGCANNNTGCCA -3' can be deduced as the protein recognition site.

Specific protein-DNA interaction at four sites flanking the chicken lysozyme gene.

Cloned DNA containing 22.2 kb of the chicken lysozyme gene region was screened with use of a nitrocellulose filter binding technique for specific recognition by nuclear DNA binding proteins from chicken oviduct cells. The analysis showed specific retention of four restriction fragments (BS1-BS4), which map approximately 6.

Evidence for the existence of two forms of RNA polymerases I and II in insect wing epidermis.

DNA-dependent RNA polymerases were solubilized from developing wings of the oak silkmoth, Antheraea pernyi, and partially purified by ion-exchange chromatography and sucrose gradient sedimentation. Four enzyme species were resolved on the basis of chromatographic behavior, divalent cation requirements, ionic strength optima, template preference and alpha-amanitin sensitivity. Each class (i.

The influence of hemolymph-binding protein on juvenile hormone stability and distribution in Manduca sexta fat body and imaginal discs in vitro.

The wing discs and fat body of Manduca sexta larvae contain enzymes (i.e. carboxylesterase and epoxide hydratase) that can convert the C18 juvenile hormone (JH) to the acid, diol and acid diol.