Abdiwali Mohamed Ali Abokor - Academia.edu (original) (raw)

Uploads

Papers by Abdiwali Mohamed Ali Abokor

Virology, 1973

Primary rat embryo and baby rat kidney cells have been transformed by human adenovirus 5 DNA. Tra... more Primary rat embryo and baby rat kidney cells have been transformed by human adenovirus 5 DNA. Transforming activity was resistant to heating (1 hr at 56 °C), and to pronase, but was sensitive to DNase. The efficiency of transformation was approximately 1 transformed focus/μg DNA.

Cell, 1990

The complete amino acid sequence of the receptor for organic calcium channel blockers (CaCB) from... more The complete amino acid sequence of the receptor for organic calcium channel blockers (CaCB) from rabbit lung has been deduced by cloning and sequence analysis of the cDNA. Synthetic RNA derived from this cDNA induces the formation of a functional CaCB-sensitive high voltage activated calcium channel in Xenopus oocytes.

Journal of Molecular Biology, 1969

The pheA gene of Corynebacterium glutamicum encoding prephenate dehydratase was isolated from a g... more The pheA gene of Corynebacterium glutamicum encoding prephenate dehydratase was isolated from a gene bank constructed in C. glutamicum. The specffic activity of prephenate dehydratase was increased six-fold in strains harboring the cloned gene. Genetic and strucetural evidence is presented which indicates that prephenate dehydratase and chorismate mutase were catalyzed by-separate enzymes in this species. The C. glutamicum pheA gene, subcloned in both orientations with respect to the Escherichia coli vector pUC8, was able to complement an E. coli pheA auxotroph. The nucleotide sequence of the C. glutamicum pheA gene predicts a 315-residue protein product with a molecular weight of 33,740. The deduced protein product demonstrated sequence homology to the C-terminal two-thirds of the bifunctional E. coli enzyme chorismate mutase-P-prephenate dehydratase.

Proceedings of The National Academy of Sciences, 1983

Science, 1987

A novel T cell receptor (TCR) subunit termed TCR delta, associated with TCR gamma and CD3 polypep... more A novel T cell receptor (TCR) subunit termed TCR delta, associated with TCR gamma and CD3 polypeptides, was recently found on a subpopulation of human T lymphocytes. T cell-specific complementary DNA clones present in a human TCR gamma delta T cell complementary DNA library were obtained and characterized in order to identify candidate clones encoding TCR delta. One cross-hybridizing group of clones detected transcripts that are expressed in lymphocytes bearing TCR gamma delta but not in other T lymphocytes and are encoded by genes that are rearranged in TCR gamma delta lymphocytes but deleted in other T lymphocytes. Their sequences indicate homology to the variable, joining, and constant elements of other TCR and immunoglobulin genes. These characteristics, as well as the immunochemical data presented in a companion paper, are strong evidence that the complementary DNA clones encode TCR delta.

We describe a simple calcium phosphate transfection protocol and neo marker vectors that achieve ... more We describe a simple calcium phosphate transfection protocol and neo marker vectors that achieve highly efficient transformation of mammalian cells. In this protocol, the calcium phosphate-DNA complex is formed gradually in the medium during incubation with cells and precipitates on the cells. The crucial factors for obtaining efficient transformation are the pH (6.95) of the buffer used for the calcium phosphate precipitation, the CO2 level (3%) during the incubation of the DNA with the cells, and the amount (20 to 30 ,ug) and the form (circular) of DNA. In sharp contrast to the results with circular DNA, linear DNA is almost inactive. Under these conditions, 50% of mouse L(A9) cells can be stably transformed with pcDneo, a simian virus 40-based neo (neomycin resistance) marker vector. The NIH3T3, C127, CV1, BHK, CHO, and HeLa cell lines were transformed at efficiencies of 10 to 50% with this vector and the neo marker-incorporated pcD vectors that were used for the construction and transduction of cDNA expression libraries as well as for the expression of cloned cDNA in mammalian cells.

Nature, 1993

When the mammalian proto-oncogene bcl-2 is overexpressed it can protect various types of cells bo... more When the mammalian proto-oncogene bcl-2 is overexpressed it can protect various types of cells both from normal and from experimentally induced apoptosis, but the molecular mechanisms involved are unknown. Although the Bcl-2 protein is membrane-associated, its subcellular location is controversial: two studies have suggested that it is mainly associated with the nuclear envelope and endoplasmic reticulum, whereas another study has suggested that it is mainly located in the inner mitochondrial membrane. The latter study has suggested that Bcl-2 might protect cells from apoptosis by altering mitochondrial function and that mitochondria may be involved in apoptosis. Here we report that human mutant cell lines that lack mitochondrial DNA (mtDNA), and therefore do not have a functional respiratory chain, can still be induced to die by apoptosis, and that they can be protected from apoptosis by the overexpression of bcl-2, suggesting that neither apoptosis nor the protective effect of bcl-2 depends on mitochondrial respiration. We also show that the Bcl-2 protein in overexpressing cells is associated with the nuclear envelope and endoplasmic reticulum, as well as with mitochondria.

Annals of the New …, 1995

Studies have been designed to examine the potential integration of DNA vaccines into the host cel... more Studies have been designed to examine the potential integration of DNA vaccines into the host cell genome. This is of concern because of the possibility of insertional mutagenesis resulting in the inactivation of tumor suppressor genes or the activation of oncogenes. The requirements for adequate testing were determined to be (1) a method to purify host cell genomic DNA from nonintegrated free plasmid, (2) a sensitive method to detect integrated plasmid in the purified genomic DNA, and (3) stringent methods to avoid contamination. These requirements were fulfilled by agarose-gel electrophoresis, the polymerase chain reaction, and separation of each activity with stringent handling procedures, respectively. An exploratory experiment was carried out in which mice were injected with 100 micrograms of vaccine plasmid DNA in each quadriceps. Examination of quadriceps and 12 other tissues at several time points failed to reveal any evidence of integration at a sensitivity level that could detect 1 to 7.5 integrations in 150,000 nuclei. A worst-case scenario determined that this would be at least 3 orders of magnitude below the spontaneous mutation frequency.

Virology, 1973

Primary rat embryo and baby rat kidney cells have been transformed by human adenovirus 5 DNA. Tra... more Primary rat embryo and baby rat kidney cells have been transformed by human adenovirus 5 DNA. Transforming activity was resistant to heating (1 hr at 56 °C), and to pronase, but was sensitive to DNase. The efficiency of transformation was approximately 1 transformed focus/μg DNA.

Cell, 1990

The complete amino acid sequence of the receptor for organic calcium channel blockers (CaCB) from... more The complete amino acid sequence of the receptor for organic calcium channel blockers (CaCB) from rabbit lung has been deduced by cloning and sequence analysis of the cDNA. Synthetic RNA derived from this cDNA induces the formation of a functional CaCB-sensitive high voltage activated calcium channel in Xenopus oocytes.

Journal of Molecular Biology, 1969

The pheA gene of Corynebacterium glutamicum encoding prephenate dehydratase was isolated from a g... more The pheA gene of Corynebacterium glutamicum encoding prephenate dehydratase was isolated from a gene bank constructed in C. glutamicum. The specffic activity of prephenate dehydratase was increased six-fold in strains harboring the cloned gene. Genetic and strucetural evidence is presented which indicates that prephenate dehydratase and chorismate mutase were catalyzed by-separate enzymes in this species. The C. glutamicum pheA gene, subcloned in both orientations with respect to the Escherichia coli vector pUC8, was able to complement an E. coli pheA auxotroph. The nucleotide sequence of the C. glutamicum pheA gene predicts a 315-residue protein product with a molecular weight of 33,740. The deduced protein product demonstrated sequence homology to the C-terminal two-thirds of the bifunctional E. coli enzyme chorismate mutase-P-prephenate dehydratase.

Proceedings of The National Academy of Sciences, 1983

Science, 1987

A novel T cell receptor (TCR) subunit termed TCR delta, associated with TCR gamma and CD3 polypep... more A novel T cell receptor (TCR) subunit termed TCR delta, associated with TCR gamma and CD3 polypeptides, was recently found on a subpopulation of human T lymphocytes. T cell-specific complementary DNA clones present in a human TCR gamma delta T cell complementary DNA library were obtained and characterized in order to identify candidate clones encoding TCR delta. One cross-hybridizing group of clones detected transcripts that are expressed in lymphocytes bearing TCR gamma delta but not in other T lymphocytes and are encoded by genes that are rearranged in TCR gamma delta lymphocytes but deleted in other T lymphocytes. Their sequences indicate homology to the variable, joining, and constant elements of other TCR and immunoglobulin genes. These characteristics, as well as the immunochemical data presented in a companion paper, are strong evidence that the complementary DNA clones encode TCR delta.

We describe a simple calcium phosphate transfection protocol and neo marker vectors that achieve ... more We describe a simple calcium phosphate transfection protocol and neo marker vectors that achieve highly efficient transformation of mammalian cells. In this protocol, the calcium phosphate-DNA complex is formed gradually in the medium during incubation with cells and precipitates on the cells. The crucial factors for obtaining efficient transformation are the pH (6.95) of the buffer used for the calcium phosphate precipitation, the CO2 level (3%) during the incubation of the DNA with the cells, and the amount (20 to 30 ,ug) and the form (circular) of DNA. In sharp contrast to the results with circular DNA, linear DNA is almost inactive. Under these conditions, 50% of mouse L(A9) cells can be stably transformed with pcDneo, a simian virus 40-based neo (neomycin resistance) marker vector. The NIH3T3, C127, CV1, BHK, CHO, and HeLa cell lines were transformed at efficiencies of 10 to 50% with this vector and the neo marker-incorporated pcD vectors that were used for the construction and transduction of cDNA expression libraries as well as for the expression of cloned cDNA in mammalian cells.

Nature, 1993

When the mammalian proto-oncogene bcl-2 is overexpressed it can protect various types of cells bo... more When the mammalian proto-oncogene bcl-2 is overexpressed it can protect various types of cells both from normal and from experimentally induced apoptosis, but the molecular mechanisms involved are unknown. Although the Bcl-2 protein is membrane-associated, its subcellular location is controversial: two studies have suggested that it is mainly associated with the nuclear envelope and endoplasmic reticulum, whereas another study has suggested that it is mainly located in the inner mitochondrial membrane. The latter study has suggested that Bcl-2 might protect cells from apoptosis by altering mitochondrial function and that mitochondria may be involved in apoptosis. Here we report that human mutant cell lines that lack mitochondrial DNA (mtDNA), and therefore do not have a functional respiratory chain, can still be induced to die by apoptosis, and that they can be protected from apoptosis by the overexpression of bcl-2, suggesting that neither apoptosis nor the protective effect of bcl-2 depends on mitochondrial respiration. We also show that the Bcl-2 protein in overexpressing cells is associated with the nuclear envelope and endoplasmic reticulum, as well as with mitochondria.

Annals of the New …, 1995

Studies have been designed to examine the potential integration of DNA vaccines into the host cel... more Studies have been designed to examine the potential integration of DNA vaccines into the host cell genome. This is of concern because of the possibility of insertional mutagenesis resulting in the inactivation of tumor suppressor genes or the activation of oncogenes. The requirements for adequate testing were determined to be (1) a method to purify host cell genomic DNA from nonintegrated free plasmid, (2) a sensitive method to detect integrated plasmid in the purified genomic DNA, and (3) stringent methods to avoid contamination. These requirements were fulfilled by agarose-gel electrophoresis, the polymerase chain reaction, and separation of each activity with stringent handling procedures, respectively. An exploratory experiment was carried out in which mice were injected with 100 micrograms of vaccine plasmid DNA in each quadriceps. Examination of quadriceps and 12 other tissues at several time points failed to reveal any evidence of integration at a sensitivity level that could detect 1 to 7.5 integrations in 150,000 nuclei. A worst-case scenario determined that this would be at least 3 orders of magnitude below the spontaneous mutation frequency.