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Biomedical subjects

Z Lev

Publications and source records attributed to Z Lev.

At least 19 recordsLinked to original sources
PubMed2000

Mutations in the beta-propeller domain of the Drosophila brain tumor (brat) protein induce neoplasm in the larval brain.

Inactivation of both alleles of the fruit fly D. melanogaster brain tumor (brat) gene results in the production of a tumor-like neoplasm in the larval brain, and lethality in the larval third instar and pupal stages. We cloned the brat gene from a transposon-tagged allele and identified its gene product. brat encodes for an 1037 amino acid protein with an N-terminal B-boxl zinc finger followed by a B-box2 zinc finger, a coiled-coil domain, and a C-terminal beta-propeller domain with six blades. All these motifs are known to mediate protein-protein interactions. Sequence analysis of four brat alleles revealed that all of them are mutated at the beta-propeller domain. The clustering of mutations in this domain strongly suggests that it has a crucial role in the normal function of Brat, and defines a novel protein motif involved in tumor suppression activity. The brat gene is expressed in the embryonic central and peripheral nervous systems including the embryonic brain. In third instar larva brat expression was detected in the larval central nervous system including the brain and the ventral ganglion, in two glands - the ring gland and the salivary gland, and in parts of the foregut - the gastric caecae and the proventriculus. A second brat-like gene was found in D. melanogaster, and homologs were identified in the nematode, mouse, rat, and human. Accumulated data suggests that Brat may regulate proliferation and differentiation by secretion/transport-mediated processes.

Amino Acid Sequence↗
PubMed2000

Utilization of K-ras mutations identified in stool DNA for the early detection of colorectal cancer.

Colorectal cancer is one of the most common malignancies in the western world. About 60,000 Americans die of colorectal cancer each year. The annual incidence rate in Israel is 40 per 100,000 persons, namely a total of 2,000 new cases each year. An important step in the progression of colorectal cancer includes induction of activating mutations in the proto-oncogene K-ras. The mutations in K-ras appear early during tumorigenesis, at the intermediate adenoma stage, and thus can be used as a biomarker for early detection in about 40% of colonic tumors. A large yet unknown number of mutated cells are shed from the developing tumor during its progression. Indeed, K-ras mutations were detected in DNA isolated from stool obtained from symptomatic and asymptomatic patients with colorectal cancer, suggesting a novel approach for a noninvasive screening procedure. However, severe difficulties in obtaining reproducible yields of amplifiable DNA from stool, and usage of nonquantitative, time-consuming procedures, hampered further progress in the utilization of K-ras mutations for the early detection of colorectal cancer. Apparently a novel protocol is required that provides reproducible output of amplifiable DNA from small amounts of stool, detects if K-ras mutated DNA is present, and determines the quantity of K-ras mutated cells in the stool sample. In addition, this protocol should be simple, robotics compatible, and thus suitable for cost-effective, large-scale mutation screening. Molecular assays for detecting K-ras mutations and additional biomarkers in stool DNA promise to be highly sensitive, specific, and cost-effective. As such they should be very effective when used in chemoprevention studies and screening protocols for colorectal cancer.

Biomarkers, Tumor↗
PubMed1996

Penile edema and meatal ulceration after intravesical instillation with bacillus Calmette-Guerin.

Bacillus Calmette-Guérin (BCG) bladder instillation is an accepted treatment modality in the management of superficial transitional cell carcinoma but is associated with frequent side effects. A report of intravesical BCG-induced penile edema and meatal ulceration that occurred in 2 patients is presented. During induction therapy, both patients complained of progressive penile edema. In 1 patient the edema appeared after the second instillation and in the other after the fourth instillation. Edema was associated with ensuing meatal ulceration and enlarged inguinal lymph nodes. BCG instillation was aborted, and oral antituberculous treatment was initiated. There was no report of external spillage during the administration of BCG or of genital or urethral trauma during catheterization. Patients were treated at different clinics but with BCG of the same strain and batch. Symptoms continued for 6 weeks until they abated. Both patients were managed with oral antituberculous drugs for a period of 3 months. Adverse effects of BCG intravesical administration affect several organs in the genitourinary system. The penis and urethra may also be involved, presenting as penile edema and meatal ulceration. Physicians who administer BCG must be familiar with the possible complications and their appropriate management.

Adjuvants, Immunologic↗
PubMed1996

The Sec1 family: a novel family of proteins involved in synaptic transmission and general secretion.

The Sec1 family, a novel family of proteins involved in synaptic transmission and general secretion, is described. To date, 14 members of this family have been identified: four yeast proteins, Sec1, Sly1, Slp1/Vps33, and Vps45/Stt10; three nematode proteins, Unc-18 and the homologues of Sly1 and Slp1; the Drosophila Rop; and six mammalian proteins, the rat Munc-18/n-Sec1/rbSec1A and rbSec1B, the mouse Munc-18b/muSec1 and Munc-18c, and the bovine Munc-18 and mSec1. The mammalian proteins share 44-63% sequence identity with the nematode Unc-18 and Drosophila Rop proteins and 20-29% with the yeast proteins and their nematode homologues. The Sec1 proteins are mostly hydrophilic and lack a transmembrane domain. Nevertheless, Sec1 proteins are found as membrane-bound proteins. Some of them are also found as soluble, cytoplasmic proteins. Binding of the rat brain Sec1 to the presynaptic membrane may be due to strong interaction with syntaxin, an integral component of this membrane. The rat brain Sec1 is also bound to Cdk5, a neural cyclin-dependent kinase. The Sec1 proteins play a positive role in exocytosis. Loss of function mutations in SEC1, SLY1, or SLP1 result in blocking of protein transport between distinct yeast sub-cellular compartments. Inactivation of unc-18 and rop results in inhibition of neurotransmitter release and, in the case of rop, inhibition of general secretion as well. In addition, studies of Rop and n-Sec1 indicate that they also play a negative role in synaptic transmission, mediated by their interaction with syntaxin. A working model addressing the dual regulative role of the Sec1 proteins in secretion is presented.

Amino Acid Sequence↗
PubMed1995

Rop and Ras2, members of the Sec1 and Ras families, are localized in the outer membranes of labyrinthine channels and vesicles of Drosophila nephrocyte, the Garland cell.

The product of the ras opposite (rop) gene is an essential component of secretion processes in Drosophila. The rop gene product is homologous to the Caenorhabditis elegans UNC-18 and the rat munc-18/n-Sec1/rbSec1 proteins, implicated in the final steps of neurotransmitter exocytosis in nerve terminals, and the bovine mSec1 protein implicated in the secretion of catecholamines in chromaffin cells. The mammalian brain protein has been shown to exert its activity in the presynaptic membrane through transient interaction with syntaxin, an integral component of this membrane. rop is highly expressed in the Drosophila nervous system, where it acts as both a positive and negative modulator of neurotransmitter release. It is also expressed in specialized tissues in which intensive exocytic/endocytic cycles take place, including the garland cells, a small group of nephrocytes which take up waste materials from the hemolymph by endocytosis. rop is regulated by a bidirectional promoter shared with Ras2, a member of the R-ras/TC21 branch of the ras supergene family. Ras2 is also highly expressed in the garland cells. These cells are characterized by their labyrinthine channels, long invaginations extending from the cell membrane, and a rich population of a variety of vesicles. In this study, we analyzed the ultrastructural localization of the Rop and Ras2 proteins in the garland cell. Rop was detected in the outer membranes of the labyrinthine channels, and in the outer membranes of many vesicles located nearby the labyrinthine channels, but not in vesicles located in inner parts of the cell. Using glutathione-S-transferase-syntaxin fusion, we show that Rop is firmly bound to syntaxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Differential expression during embryogenesis of three genes clustered in the Ras1 region of Drosophila melanogaster.

Transcription mapping and nucleotide sequence analysis reveal that the genomic region of the Drosophila Ras1 gene contains a cluster of three closely localized genes. A gene termed Rlb1 is located nearby and upstream of Ras1, and is oriented in the opposite polarity relative to Ras1. In addition, a third gene termed Rlc1, is found at a very close proximity downstream to Rlb1. Ras1, the homologue of the human transforming ras genes, has been shown to be active in the posterior termini of the Drosophila embryo and in the eye imaginal disc in pathways of cell fate determination. We demonstrate that during embryogenesis Ras1 transcripts are restricted mainly to the embryonic central nervous system, suggesting that the gene product also may have a role in these nerve cells. Rlb1 encodes for a novel, lysine-rich basic protein. It is expressed mainly in the developing midgut and in the somatic mesoderm. Rlc1 also encodes for a novel, basic protein. The expression of Rlc1 during embryogenesis is similar, but not identical, to the expression pattern detected for Ras1. The vertebrate p21Ras proteins are bound to the inner face of the cell membrane. Ras1, the Drosophila homologue of p21, and the Rlb1 protein, are also non-cytoplasmic, membranous proteins. Rlb1 is found in the cell membrane of larval midgut epithelial cells. In addition, Rlb1 is detected in the nuclei of these cells, and in the nuclei of the midgut imaginal cells.

Amino Acid Sequence↗
PubMed1994

rop, a Drosophila homolog of yeast Sec1 and vertebrate n-Sec1/Munc-18 proteins, is a negative regulator of neurotransmitter release in vivo.

The mammalian homolog of the yeast Sec1p, n-Sec1/Munc-18 has been demonstrated to bind the presynaptic membrane protein syntaxin, a putative synaptic vesicle docking protein. To determine the role of n-Sec1/Munc-18 in neurotransmitter release in vivo, we have overexpressed the Drosophila homolog, rop, in third instar larvae and measured the electrophysiological consequences at the neuromuscular junction. A 3- to 5-fold induction of the rop protein causes a dramatic decrease in neurotransmitter release, suggesting rop may restrict the ability of vesicles to dock or of docked vesicles to fuse. Consistent with this hypothesis, rop overexpression also reduces the number of spontaneous vesicle fusions by more than 50%, and repetitive stimulation results in significant decreases in evoked responses similar to those observed in rab3a mutant mice. However, rop overexpression does not alter significantly the Ca2+ dependence of neurotransmitter release. We propose that the Drosophila n-Sec1/Munc-18 homolog plays a negative role in neurotransmitter release in vivo, in addition to its previously identified positive function, possibly by modulation of docking of synaptic vesicles or activation of a pre-fusion complex at the active zone.

Animals↗
PubMed1993

The Drosophila Ras2 and Rop gene pair: a dual homology with a yeast Ras-like gene and a suppressor of its loss-of-function phenotype.

The promoter of the Drosophila melanogaster Ras2 gene is bidirectional, regulating an additional gene oriented in the opposite polarity. The two divergently transcribed genes are only 93 bases apart and deletion analysis proved that common cis-acting elements within this promoter region are required for the transcriptional activity of both genes. We cloned the gene paired with Ras2 in the bidirectional promoter and isolated cDNAs corresponding to its mRNA. The Ras opposite (Rop) gene encodes for a 68 x 10(3) M(r) protein which shares sequence homology with the members of a novel Saccharomyces cerevisiae gene family, including the SLY1, SEC1 and VPS33 (SLP1) genes, all of which are involved in vesicle trafficking among yeast cellular compartments. A highly conserved motif in this family is also found in beta-COP, a coat protein isolated from rat Golgi-bound nonclathrin vesicles. Thus, the Rop protein may be a component of one of the vesicle trafficking pathways in Drosophila cells. The Rop gene expression during embryogenesis is restricted to the central nervous system (CNS) and the garland cells, a small group of nephrocytes that takes up waste materials from the haemolymph by endocytosis. Ras2 is also expressed in the embryonic garland cells. In postembryonic stages, the two genes are co-expressed in the larval salivary glands and the central nervous system, and in the adult CNS and reproductive systems. Interestingly, the S. cerevisiae SLY1-20 allele is a suppressor of the loss of the YPT1 gene, a ras-like gene implicated in vesicle translocation, suggesting that the two genes may interact with one another. Since Sec1p and beta-COP may also interact with small GTP-binding proteins of the ras superfamily, it is conceivable that the Rop and Ras2 gene products are not just co-expressed in common tissues, but may also functionally interact with one another in these tissues.

Amino Acid Sequence↗
PubMed1989

Maternal and embryonic transcripts of Drosophila proto-oncogenes are expressed in Schneider 2 culture cells but not in l(2)gl transformed neuroblasts.

The transcription patterns of Drosophila melanogaster src, abl and two ras homologs were analyzed in normal Drosophila tissue, in neuroblasts derived from tumorous larval brain of the mutant lethal(2)giant larvae [l(2)gl] and in Schneider 2 tissue culture cells. Our results show that, in addition to constitutive transcripts, the src, abl, ras1 and ras3 genes express a set of maternal/embryonic-specific transcripts. By using these transcripts as differentiation markers we show that, in spite of their embryonic-like, undifferentiated phenotype, the l(2)gl transformed neuroblasts are authentic larval cells. Using the same criterion the Schneider 2 tissue culture cells show the characteristics of embryonic cells.

Animals↗
PubMed1988

A bidirectional promoter is regulating the Drosophila ras2 gene.

We isolated and delimitated the Drosophila ras2 promoter region, determined its sequence and mapped the transcription units expressed in this region. The results showed that the Drosophila ras2 gene is flanked by another transcription unit, which codes for two larger transcripts, 2.5 and 2.9 kb long. Orientation experiments, in which sense and antisense RNA probes were used, revealed that both these and the ras2 transcripts are synthesized from different DNA strands. Thus, the flanking transcription unit is in the opposite polarity relative to the ras2 gene. The transcription start sites of the ras2 gene and the flanking transcription unit were determined by external primer extension with T4 DNA polymerase and by RNAase-protection assay and were found to be only 94 nucleotides apart. Apparently, the Drosophila ras2 promoter is a bidirectional promoter. Nucleotide sequence analysis revealed that the 5'-end of the ras2 transcript is within an inverted repeat of the insect cap box. TATA- and GC-like boxes were also found. Analysis of direct and inverted repeats in the promoter region suggested that it is asymmetrical. To demonstrate promoter activity, each side of the ras2 bidirectional promoter was fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and tested by transfecting Drosophila Schneider 2 culture cells. Significant CAT activity was obtained with both transcription fusions.

Animals↗
PubMed1987

A procedure for large-scale isolation of RNA-free plasmid and phage DNA without the use of RNase.

A preparative procedure for the large-scale isolation of plasmid DNA without the use of RNAse is described. Crude plasmid DNA is prepared using a standard boiling method. High-molecular-weight RNA is removed by precipitation with LiCl, and low-molecular-weight RNA is removed by sedimentation through high-salt solution. The procedure is inexpensive, rapid, simple, and particularly suitable for processing several large-scale preparations simultaneously. A similar procedure has been developed for preparation of lambda-phage DNA.

Bacteriophage lambda↗
PubMed1985

Developmental changes in expression of the Drosophila melanogaster epidermal growth factor receptor gene.

A Drosophila gene homologous to the human EGF receptor gene has recently been isolated and sequenced. Two transcripts, 7.6- and 7.1-kb long, encoded by this gene were identified in Drosophila melanogaster. The transcripts are present at low abundance in the maternal RNA stored in unfertilized eggs and in 2-hr-old embryos. The abundance of both transcripts increases sharply between 2 and 5 hr after egg deposition, it remains high throughout embryogenesis, and decreases again in the larval and pupal stages. In adult flies the two transcripts are expressed differentially. The 7.1-kb transcript is present during adulthood at the same level detected previously in pupal stage, but the abundance of the 7.6-kb transcript decreases substantially and it remains low during adulthood.

Animals↗
PubMed1985

Expression of ras cellular oncogenes during development of Drosophila melanogaster.

The transcription patterns of three v-Ha-ras-related cellular oncogenes in Drosophila melanogaster were studied. Each gene coded for at least two distinct transcripts. The larger transcript of each gene was expressed at a similar abundance during the entire life cycle of fruit flies, whereas the shorter transcripts were much more abundant in embryonic stages than at later stages.

Animals↗
PubMed1984

Expression of the src and abl cellular oncogenes during development of Drosophila melanogaster.

Transcription of the Drosophila homologs of the abl and src cellular oncogenes, termed Dash and Dsrc , respectively, was studied. Despite the fact that Dash and Dsrc share sequence homology, they have distinct patterns of transcription during development. The Dash transcript, 6.2 kilobases long, is found in maternal RNA stored in unfertilized eggs and in embryos up to 4 h after egg laying. In contrast, Dsrc transcripts are 3.2, 4.8, and 5.2 kilobases long. They are detected in eggs and embryos and to a lesser extent in larvae and adult flies. The relative amount of each of the three Dsrc transcripts changes during the different stages of development.

Animals↗
PubMed1980

Four sizes of transcript produced by a single sea urchin gene expressed in early embryos.

This report concerns a set of sea urchin egg and embryo transcripts complementary to a single-copy region of a cloned DNA fragment (Sp88). Three distinct 16-cell embryo polysomal RNA species were found to hybridize with this fragment. These RNAs are about 1700, 3000, and 4000 nucleotides (nt) in length, and the same species were identified in unfertilized eggs. A significant fraction of all three species of the egg and early embryo transcripts is polyadenylylated. At gastrula stage Sp88 transcripts are almost completely confined to the nucleus [Lev, Z., Thomas, T. L., Lee, A. S., Angerer, R. C., Britten, R. J. & Davidson, E. H. (1980) Dev. Biol, 75, in press]. The Sp88 transcripts of gastrulae are present as a fourth RNA species approximately 5800 nt in length. The four species share a sequence element of cloned DNA fragment that is about 1000 nt long. These RNAs constitute a set of alternative partially overlapping transcripts from the same genomic region.

Animals↗