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B S Shastry

Publications and source records attributed to B S Shastry.

84 records · Page 5Linked to original sources
PubMed1983

Multiple forms of DNA-dependent RNA polymerases in Xenopus laevis. Rapid purification and structural and immunological properties.

DNA-dependent RNA polymerases I, II, and III (EC 2.7.7.6) were isolated from Xenopus laevis ovaries. The soluble enzymes were precipitated with polyethyleneimine and subjected to chromatography on heparin-Sepharose, DEAE-Sephadex, and phosphocellulose. RNA polymerase I was subjected to an additional chromatographic step on CM-Sephadex. The procedure required 40 h and produced purified RNA polymerase forms IA, IIA, and III in yields of 5 to 40%. The specific activities of RNA polymerases IIA and III (on native DNA) were comparable to those reported from other eukaryotic sources, whereas that of form IA was severalfold greater than the specific activities reported for other purified class I RNA polymerases. The complex subunit compositions of chromatographically purified RNA polymerases IA, IIA, and III were distinct when analyzed by polyacrylamide gradient gel electrophoresis under denaturing conditions, although all three classes contained polypeptides with Mr = 29,000, 23,000, and 19,000. Antibodies prepared against RNA polymerase III showed common antigenic determinants within the class I, II, and III enzymes. The sites responsible for the cross-reaction are located, at least in part, on the common 29,000-dalton polypeptide.

Animals↗
PubMed1982

Multiple factors involved in the transcription of class III genes in Xenopus laevis.

Cell-free extracts from Xenopus laevis oocytes (ovarian tissue), unfertilized eggs, embryos, and cultured kidney cells direct accurate transcription of cloned 5 S RNA and tRNA genes. Fractionation of these extracts by conventional ion exchange chromatography shows that multiple components are essential for the transcription of each of these genes by RNA polymerase III. Two chromatographically distinct fractions from ovary, egg, embryo, and kidney cell extracts are necessary and sufficient, in the presence of purified RNA polymerase III, for the transcription of tRNA genes. Transcription of 5 S RNA genes requires components present in these same fractions as well as the previously described 5 S gene-specific factor (TFIIIA). The analogous chromatographic fractions from different tissue extracts are functionally interchangeable, consistent with the suggestions that the endogenous factors which are necessary and sufficient for purified gene transcription are general (and not tissue-specific) factors.

Animals↗
PubMed1981

The binding of a transcription factor to deletion mutants of a 5S ribosomal RNA gene.

A transcription factor binds specifically to a region within the 5S ribosomal RNA gene that is known to be required for accurate initiation of transcription of the gene. We have confirmed the significance of this interaction by comparing various deletion mutants for their ability to initiate transcription and to bind the protein. Loss of specific binding of the protein occurs when the gene is deleted beyond +83 from the 3' direction. This coincides exactly with the loss of ability to initiate transcription. In contrast, deletions entering the gene from the 5' direction and extending beyond the 5' border of the control region (+50/+55) give partial protection of the remainder of the control region. This observation can explain why deletions beyond the 5' border of the control region that are unable to initiate transcription can still compete for the transcription of the wild-type 5S RNA gene.

Animals↗
PubMed1980

Specific interaction of a purified transcription factor with an internal control region of 5S RNA genes.

A factor necessary for the accurate transcription of cloned Xenopus 5S genes in vitro has been isolated from soluble extracts of X. laevis ovaries. The activity of the factor was monitored by its ability to facilitate transcription of exogenous 5S genes in unfertilized egg extracts which are otherwise incompetent for 5S gene transcription. The factor was purified via ion exchange chromatography, and apparently consists of a 37,000 dalton polypeptide. This factor is necessary for the transcription of both the oocyte-type and somatic-type 5S genes of Xenopus, but is not required for, and has no detectable effect upon, the transcription of a cloned Xenopus tRNA1Met gene. The site of action of the factor has been investigated using the "footprinting" method of Galas and Schmitz (1978). The factor binds specifically to intragenic regions extending, approximately, from nucleotide positions 45 to 96 on both somatic and oocyte-type 5S genes. Additionally, this binding occurs independently of, and is not altered by, the presence of purified RNA polymerase III or unfertilized egg extracts. The probable role of this factor in transcription initiation is discussed.

Animals↗
PubMedDate not supplied

Lack of association of the Norrie disease gene with retinoschisis phenotype.

PURPOSE: It has been reported recently that mice carrying a disrupted Norrie disease gene produced alterations in the murine eye that are similar to congenital retinoschisis. Therefore, it was of interest to determine whether mutations in the Norrie disease gene can account for the disease in families with retinoschisis that do not carry mutations in the retinoschisis gene. METHODS: The patient set comprised 5 cases of retinoschisis (1 familial and 4 sporadic), all unrelated to each other. Fundus examination of affected individuals showed foveal and peripheral schisis, and the visual acuity range was 20/40-20/60. Peripheral blood specimens were collected from affected and unaffected family members. DNA was extracted and amplified by polymerase chain reaction amplification of exons of the Norrie disease gene. The amplified products were sequenced by the dideoxy chain termination method. RESULTS: The data revealed no disease-specific sequence alterations in the Norrie disease gene. CONCLUSION: Although we cannot completely exclude the possibility of the Norrie disease gene as a candidate gene, the above results suggest that the structural and functional changes in the Norrie disease gene are not associated with clinically typical retinoschisis families that do not contain mutations in the coding regions and splice sites of the retinoschisis gene.

DNA Mutational Analysis↗
PubMedDate not supplied

Pharmacogenetics and the concept of individualized medicine.

Adverse drug reaction in patients causes more than 2 million hospitalizations including 100,000 deaths per year in the United States. This adverse drug reaction could be due to multiple factors such as disease determinants, environmental and genetic factors. In order to improve the efficacy and safety and to understand the disposition and clinical consequences of drugs, two rapidly developing fields--pharmacogenetics (focus is on single genes) and pharmacogenomics (focus is on many genes)--have undertaken studies on the genetic personalization of drug response. This is because many drug responses appear to be genetically determined and the relationship between genotype and drug response may have a very valuable diagnostic value. Identification and characterization of a large number of genetic polymorphisms (biomarkers) in drug metabolizing enzymes and drug transporters in an ethnically diverse group of individuals may provide substantial knowledge about the mechanisms of inter-individual differences in drug response. However, progress in understanding complex diseases, its negative psychosocial consequences, violation of privacy or discrimination, associated cost and availability and its complexity (extensive geographic variations in genes) may become potential barriers in incorporating this pharmacogenetic data in risk assessment and treatment decisions. In addition, it requires increased enthusiasm and education in the clinical community and an understanding of pharmacogenetics itself by the lay public. Although individualized medications remain as a challenge for the future, the pharmacogenetic approach in drug development should be still continued. If it becomes a reality, it delivers benefits to improve public health and allow genetically subgroup diseases thereby avoiding adverse drug reactions (by knowing in advance who should be treated with what drug and how).

Cytochrome P-450 Enzyme System↗
PubMedDate not supplied

Coats' disease and congenital retinoschisis in a single eye: a case report and DNA analysis.

The clinical features of Coats' disease and congenital retinoschisis (RS) are distinctly different. Therefore, finding changes consistent with Coats' disease and congenital RS in a single eye is an unusual occurrence. The following report describes two cases with a Coats' telangiectatic lesion in one region of the retina separated by normal retina and the presence of central and peripheral congenital RS. Molecular genetic analysis of the Norrie disease and RS genes failed to identify disease-causing or polymorphic mutations in either of the genes, suggesting that the above condition is clinically and genetically a different disorder. Further studies are needed to identify the genes responsible for the above disorder and associated ocular manifestations.

Child, Preschool↗
PubMedDate not supplied

Evaluation of the norrie disease gene in a family with incontinentia pigmenti.

Incontinentia pigmenti (IP) is an ectodermal multisystem disorder which can affect dental, ocular, cardiac and neurologic structures. The ocular changes of IP can have a very similar appearance to the retinal detachment of X-linked familial exudative vitreoretinopathy, which has been shown to be caused by the mutations in the Norrie disease gene. Therefore, it is of interest to determine whether similar mutations in the gene can account for the retinal pathology in patients with IP. To test our hypothesis, we have analyzed the entire Norrie disease gene for a family with IP, by single strand conformational polymorphism followed by DNA sequencing. The sequencing data revealed no disease-specific sequence alterations. These data suggest that ocular findings of IP are perhaps associated with different genes and there is no direct relationship between the genotype and phenotype.

DNA↗
PubMedDate not supplied

Norrie disease and exudative vitreoretinopathy in families with affected female carriers.

PURPOSE: Norrie disease (ND) is a rare X-linked recessive disorder characterized by congenital blindness, which is often associated with sensorineural hearing loss and mental retardation. X-linked familial exudative vitreoretinopathy (FEVR) is a hereditary disorder characterized by an abnormality of the peripheral retina and is not associated with systemic diseases. X-linked recessive disorders generally do not affect females. Here we show that female carriers can be associated with manifestation of an X-linked disorder. METHODS: A four-generation family with an affected female, and a history of congenital blindness and hearing loss, was identified through the pro-band. A second family, with a full-term female infant, was evaluated through ophthalmic examinations and found to exhibit ocular features, such as retinal folds, retinal detachment and peripheral exudates. Peripheral blood specimens were collected from several affected and unaffected family members. DNA was extracted and analyzed by single-strand conformation polymorphism (SSCP) following polymerase chain reaction (PCR) amplification of the exons of the Norrie disease gene. The amplified products were sequenced by the dideoxy chain termination method. RESULTS: In an X-linked four-generation family, a novel missense (A118D) mutation in the third exon of the Norrie disease gene, was identified. The mutation was transmitted through three generations and cosegregated with the disease. The affected maternal grandmother and the unaffected mother carried the same mutation in one of their alleles. In an unrelated sporadic family, a heterozygous missense mutation (C96Y) was identified in the third exon of the Norrie disease gene in an affected individual. Analysis of exon-1 and 2 of the Norrie disease gene did not reveal any additional sequence alterations in these families. The mutations were not detected in the unaffected family members and the 116 normal unrelated controls, suggesting that they are likely to be the pathogenic mutations. CONCLUSIONS: The results further strengthen the proposal that X-linked disorders can occur in female carriers, due likely to an unfavorable X-inactivation.

Blindness↗