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B S Shastry

Publications and source records attributed to B S Shastry.

At least 73 records · Page 4Linked to original sources
PubMed1993

Gene expression: surprises from the class III side.

Those genes which are transcribed by RNA polymerase III continue to give surprising results with respect to their cis-acting elements and transacting factors. As a result, a broader view of class III promoters has emerged and the internal promoters are not universal in classical polymerase III genes. The involvement of TFIID, TFIIA, a factor homologous to TFIIB and an RNA factor in class III gene transcription has further changed our thinking in regards to the mechanisms of transcription.

Animals↗
PubMed1993

Mapping studies of an X-linked familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a congenital hereditary, bilateral eye disorder which affects both retina and the vitreous body. As a first step toward the identification of the gene responsible for the X-linked disorder, we report here the results of DNA analyses from the patients and their parents of two families having members affected with FEVR. The results indicate that loci MIC2 and choroideremia are unlikely to be associated with the disease. Similar results are obtained with anonymous probes DXS7 and DXYS1 and microsatellite markers DXS426, DXS453 and DXS454. No signs of microdeletion, substitution and rearrangements in these loci could be detected. These data suggest that the above loci are probably not involved in determining the FEVR pathology.

Alleles↗
PubMed1993

Studies on class III gene transcription.

In an attempt to understand the functional role of individual transcription factors, we have carried out S1 nuclease analyses of in vitro synthesized RNA using partially purified HeLa cell factors and truncated 5S and tDNA. The results indicate that faithful initiation of 5S gene transcription depends on the presence of IIIA, IIIB and IIIC in addition to RNA polymerase III. On the other hand, tDNA transcription initiation requires IIIB and IIIC and RNA polymerase III. In addition, we found that either 'A' block promoter or 'B' block alone can not serve as a template for the initiation of tDNA transcription. When an ultraviolet irradiated 5S DNA was used as a template, transcription is minimally affected at a lower dose suggesting that small differences in the helical structure may not have much effect on the transcription machinery. These results along with an in vitro attempt to reproduce Xenopus 5S RNA gene regulation are presented.

Animals↗
PubMed1992

X-linked recessive familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy is an inherited disorder characterized by retinal traction, peripheral vitreous opacities, and subretinal and intraretinal exudates. We observed a family in which four boys (the children of three sisters) were affected with this disorder and an X-linked recessive inheritance was apparent. The differential diagnosis includes retinopathy of prematurity, primary hyperplastic primary vitreous, Coats' disease, peripheral uveitis, retinoblastoma, and Norrie's disease, but this differentiation can usually be made on the basis of clinical findings alone. Knowledge of X-linked recessive transmission is important for correct diagnosis and for genetic counseling.

Child, Preschool↗
PubMed1991

The assembly of functional preinitiation complexes and transcription of 5S RNA-encoding genes containing point mutations.

The transcription of several Syrian hamster 5S RNA-encoding genes (5S genes) containing single and multiple point mutations in and around the intragenic control region has been analyzed in a HeLa cell-free system. Although most genes with point mutations displayed normal levels of transcription, several exhibited a three- to fivefold reduction in transcription. These mutations interfere with the interaction between the 5S genes and the soluble factors. The above studies help to establish the importance of specific nucleotides within the 5S gene for productive interactions of individual transcription factors in vitro.

Animals↗
PubMed1991

Xenopus transcription factor IIIC (TFIIIC) specifically interacts with the "B" block region of the TFIIIA gene.

Transcription factors IIIC (TFIIIC), TFIIIB and RNA polymerase III are commonly required for class III gene transcription in vitro. To understand the diversity and specificity of Xenopus TFIIIC, we have further characterized this factor. Our analyses indicate that a partially purified TFIIIC fraction contains an activity which specifically recognizes the "B" block element of TFIIIA gene. Stable complex formation assays with HeLa cell extracts demonstrate that the TFIIIA gene can stably sequester TFIIIC. off

Animals↗
PubMed1991

Xenopus transcription factor IIIA (XTFIIIA): after a decade of research.

Xenopus transcription factor IIIA (XTFIIIA) is the first eukaryotic transcription factor purified to homogeneity and is specifically required for the 5S RNA gene transcription. It contains two structural domains and nine zinc finger motifs through which it recognizes the promoter region of the 5S RNA gene. It also binds to 5S RNA and serves to store 5S RNA in the form of 7S ribonucleoprotein particles in oocytes. Additionally, it forms a metastable complex with 5S DNA and promotes the formation of stable and competent transcription complexes. Its expression is developmentally controlled at the level of transcription and translation. Moreover, it participates in the assembly of active chromatin templates and at least, in part, is responsible for the developmental regulation of two kinds of 5S RNA genes in Xenopus.

Animals↗
PubMed1991

Analysis of eye lens-specific genes in congenital hereditary cataracts and microphthalmia of the miniature schnauzer dog.

The congenital hereditary cataracts and microphthalmia in the miniature schnauzer dog are inherited by an autosomal recessive mode. To understand the genetic basis of these diseases, the authors purified and analyzed leukocyte deoxyribonucleic acid (DNA) from affected and normal animals using a candidate gene approach. Because the genes that encode the lens-specific proteins, specifically, alpha, beta, and gamma crystallins and the membrane protein (MP26), are known to maintain the structure and function of the lens, the authors used complimentary DNA (cDNA) fragments that corresponded to the above genes to search for the mutations at their loci in the affected animals. They found no evidence of the gene deletion and rearrangement in any of the five loci. In addition, the hybridizable sequences of the dog DNA to the specific probes for the human chromosome 4 and 18 loci, which are reported to be involved in the abnormality of the human eye, seem to be unaffected. These data support the notion that the hereditary cataracts and microphthalmia in the dog may be associated with genes other than those reported for several animal systems.

Animals↗
PubMed1990

Specific interaction of a partially purified Xenopus transcription factor IIIC (TFIIIC) with frog tRNA gene.

Transcription factor IIIC (TFIIIC) from Xenopus has been partially purified and characterized. Footprinting analyses indicate that a partially purified TFIIIC fraction contains an activity which specifically recognizes the "B" block element of tRNA gene. In addition, two other regions located downstream from the "B" block sequence are also protected. Protection experiments on 5S genes by DNAase I with either TFIIIC alone or TFIIIA and TFIIIC produced a minimal change in the cleavage pattern implying that TFIIIC does not intimately associate with DNA. The implications of these findings in relation to the class III gene transcription are discussed.

Animals↗
PubMed1990

Isolation and characterization of a distantly related member of the beta-gamma crystallin super gene family from Xenopus.

In an attempt to isolate gamma crystallin genes from Xenopus genomic library, we have obtained seventeen clones which strongly hybridized to the gamma 1 cDNA probe from Rana temporaria. Of these four clones are characterized. A restriction map was derived by using single and multiple digests with a variety of enzymes. Hybridization selection of lens mRNAs and in vitro translation produced a protein of 26,000 daltons. These data suggest that the above clones may contain at least part of the gamma or beta crystallin sequences.

Animals↗
PubMed1990

The structure and expression of a distantly related member of the beta-gamma crystallin super gene family from Xenopus.

In an attempt to understand amphibian crystallin gene regulation, we have isolated and partially characterized several genomic clones which hybridized to the gamma 1 cDNA probe from Rana temporaria. A complete sequence of one of these clones showed slight homology to the mammalian beta and gamma crystallins. The deduced amino acid sequence of the coding region and its alignment as a folding unit indicated that all the topologically equivalent residues involved in maintaining the protein folding pattern are highly conserved. Northern blot analysis of total RNAs derived from several adult tissues, including eye lens, suggested that an RNA of approximately 700 nucleotides long is present in lens, heart, spleen and embryos of later stages of development but not in retina, oocytes and embryos of early developmental stages.

Amino Acid Sequence↗
PubMed1989

Transcription of 5S RNA genes containing insertion mutation and the assembly of preinitiation complexes.

The transcription of Xenopus 5S RNA genes containing insertions in and around the intragenic control region has been analyzed in a HeLa cell-free system. A 15 bp insertion within the intragenic region greatly diminished binding of TFIIIA and concomitantly reduced binding of TFIIIB and transcription in vitro. This study helps to define more precisely the promoter organization of Xenopus 5S RNA genes for the efficient interactions with transcription factors.

Animals↗
PubMed1989

Immunological studies on gamma crystallins from Xenopus: localization, tissue specificity and developmental expression of proteins.

In an effort to understand the spatio-temporal regulation of crystallins and their genes during lens development, the gamma crystallins from the frog lens have been isolated, purified and characterized. Using an immunological approach, they were found to be localized exclusively in the lens fiber cells and were not detected in any other lens cells or non-lens tissues including mature oocytes. During embryogenesis, the antigens were first detected in stage 25 embryos (but not in stage 20 embryos). Their level first decreased and then increased during subsequent stages of development. A different member of the family was also found to be expressed during later stages of embryogenesis.

Animals↗
PubMed1986

The use of monoclonal antibody to study the functional properties of RNA polymerase II subunits.

Monoclonal antibodies were raised in mouse against purified calf thymus RNA polymerase II. Three stable hybridoma lines were identified and found to secrete IgM type antibodies. The antibody produced by one clone was found to be directed against the large subunits (IIb and IIc) of the enzyme. In an immuno-blot of electrophoretically separated subunits the monoclonal antibody recognised antigenic determinant on the largest polypeptides of several eukaryotic RNA polymerases II tested. In an in vitro transcription system, this antibody is found to inhibit the specific transcription from the adenovirus major late promoter only when the extract is preincubated with the antibody in the absence of DNA.

Animals↗
PubMed1986

5S RNA gene specific transcription factor (TFIIIA) changes the linking number of the DNA.

The purified 5S gene specific transcription factor A (TFIIIA), when incubated with the relaxed 5S gene in the presence of topoisomerase I alters the conformation of the DNA, resulting in a change in the linking number. This interaction introduces a change of one bp per TFIIIA binding site at a low concentration of DNA to protein (1:2) which increases to an extent of 0.9 turns (9 bp) per TFIIIA binding site at a higher protein concentration (1:12). These analyses support the notion that the binding of TFIIIA to the 5S DNA introduces a minimal change in the topology of circular DNA molecules.

Animals↗
PubMed1984

Altered levels of a 5 S gene-specific transcription factor (TFIIIA) during oogenesis and embryonic development of Xenopus laevis.

Xenopus laevis oocytes contain a 38,000-Da protein which serves both as a 5 S gene-specific transcription initiation factor (TFIIIA) and to stabilize 5 S RNA in ribonucleoprotein complexes. Using an antibody to this protein we have measured the levels of TFIIIA during oogenesis and embryonic development in X. laevis. The maximal steady state level (approximately 10(12) molecules/oocyte) is reached early in oogenesis but drops 10- to 20-fold in later stages and another 10- to 20-fold during ovulation. The reduced amount present in the unfertilized egg remains at a nearly constant level throughout early development, but with cell division the cellular concentration drops from 3 X 10(9) to about 10(4) molecules/cell. An immunoreactive protein of the same size is also found in liver tissues and in cultured kidney cells, which also contain about 10(4) molecules/cell. By both structural (CNBr peptide analysis) and functional (transcription of 5 S genes) analyses the embryonic and kidney cell 38,000-Da factors appear indistinguishable from oocyte TFIIIA. In addition a second antigenically related protein of about 40,000 Da is found in late stage embryos, liver tissues, and adult kidney cells (where it is severalfold more abundant than the 38,000-Da TFIIIA). The chromatographic fractionation and functional analysis of the kidney cell extracts has shown that fractions containing the 38,000-Da protein support 5 S RNA synthesis while fractions containing the 40,000-Da protein do not. The significance of these findings for 5 S gene regulation is discussed with respect to the dual function of TFIIIA, the presence of rate-limiting amounts of TFIIIA, and the possibility of stage-specific factors.

Animals↗