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At least 109 records · Page 6Linked to original sources
PubMed1991

The 5' noncoding region sequence of the Choristoneura biennis entomopoxvirus spheroidin gene functions as an efficient late promoter in the mammalian vaccinia expression system.

About 100 nucleotides of DNA sequence at the 5' noncoding region of the Choristoneura biennis entomopoxvirus spheroidin gene was chemically synthesized and inserted into a vaccinia expression vector, interrupting the vaccinia thymidine kinase gene. When the bacterial beta-galactosidase gene was introduced downstream of this sequence and a recombinant vaccinia virus containing these inserts was obtained by homologous recombination, beta-galactosidase was shown to be expressed at a high level late in the vaccinia infection cycle. The level of beta-galactosidase expression was four- to fivefold higher with this spheroidin-vaccinia recombinant virus than with a similar recombinant in which the beta-galactosidase gene was under the control of the vaccinia 7.5-kDa promoter. Primer extension and S1 mapping of the 5' terminus of the beta-galactosidase transcript located the transcription initiation site within the spheroidin DNA sequence, confirming the promoter nature of this DNA sequence in the vaccinia system. Dot blot analysis indicated that the difference in beta-galactosidase expression with these two recombinant viruses can be attributed to the difference in their transcript levels. We also demonstrated that full promoter activity encoded in the spheroidin 5' noncoding sequence was contained within a 38-nucleotide DNA fragment.

Animals↗
PubMed1986

Transcriptional control of herpesvirus gene expression: gene functions required for positive and negative regulation.

We have used an in vitro nuclear run-off assay to measure the levels of transcription of specific herpes simplex virus genes at different times during a lytic infection. We analyzed the effects of inhibition of DNA replication and of defects in two herpes simplex virus regulatory proteins on the transcription of these genes. We present evidence that the transcription of the alpha ICP4 gene is negatively regulated during a lytic infection. The regulation of ICP4 gene transcription requires the beta protein ICP8 (where ICP = infected cell polypeptide). Transcription of the beta ICP8, gamma 1 ICP5, and gamma 2 glycoprotein C (gC) genes was dependent on ICP4, and transcription of the gamma 2gC gene was strongly inhibited when DNA replication was blocked. Defects in ICP8 also resulted in increased levels of transcription of the ICP4, ICP8, ICP5, and gC genes from parental viral genomes. Our results suggest that ICP8 may be important in maintaining the highly ordered cascade of viral gene expression.

DNA Replication↗
PubMed1988

Characterization of rat and human tyrosine hydroxylase genes: functional expression of both promoters in neuronal and non-neuronal cell types.

We describe the structure of the promoter and intron 1 of the human and rat tyrosine hydroxylase genes. The 5' flanking region of the two genes are 74% identical (+1 to -380) and contain a completely conserved cAMP response element. Although both genes are single copy, multiple splicing events of the human transcript lead to multiple mRNAs. Based on several lines of evidence alternative forms of mRNA of rat TH analogous to those in the human are not present. Both rat and human promoters direct the transcription of reporter genes when introduced into rat pheochromocytoma and fibroblast cells.

Adrenal Gland Neoplasms↗
PubMed1989

Analysis of rev gene function on human immunodeficiency virus type 1 replication in lymphoid cells by using a quantitative polymerase chain reaction method.

Most detailed analyses of the human immunodeficiency virus type 1 (HIV-1) rev gene product have relied on transfection of subgenomic env constructs into cells in which amplification of the transfected DNA occurs. This was necessitated by difficulties in quantitating low-abundance HIV-1 mRNA species and in distinguishing different RNAs of similar sizes. We have modified the conventional polymerase chain reaction method for general use as an extremely sensitive procedure for quantitative analysis of RNA species. Using this method, we assessed the role of the HIV-1 rev gene in viral replication following mutagenesis of an infectious molecular clone, HIV-1JR-CSF. Following transfection of wild-type and mutant proviral constructs, we can specifically detect unspliced RNA and distinguish between the spliced tat-rev and nef mRNAs, which are not resolved by standard RNA analyses. Our results show that the rev protein of HIV-1JR-CSF simultaneously down regulates the expression of tat-rev and nef RNAs and up regulates the level of unspliced full-length HIV-1 RNA. A cis-acting element(s), located exclusively within the env sequences, is essential to exhibit this regulation. Fractionation of cells shows that the ultimate effect of Rev is to direct the appearance of unspliced or singly spliced RNAs in the cytoplasm. Models are discussed for possible mechanisms of Rev action.

Base Sequence↗
PubMed1990

Drosophila ribosomal RNA genes function as an X-Y pairing site during male meiosis.

In Drosophila melanogaster males, the sex chromosomes pair during meiosis in the centric X heterochromatin and at the base of the short arm of the Y (YS), in the vicinity of the nucleolus organizers. X chromosomes deficient for the pairing region segregate randomly from the Y. In this report we show that a single ribosomal RNA (rRNA) gene stimulates X-Y pairing and disjunction when inserted onto a heterochromatically deficient X chromosome by P element-mediated transformation. We also show that insert-containing X chromosomes pair at the site of insertion, that autosomal rDNA inserts do not affect X-Y pairing or disjunction, and that the strength of an X pairing site is proportional to the dose of ectopic rRNA genes. These results demonstrate that rRNA genes can promote X-Y pairing and disjunction and imply that the nucleolus organizers function as X-Y pairing sites in wild-type Drosophila males.

Animals↗
PubMed1988

Cytotoxic T lymphocyte response to minor H-43a alloantigen in H-43b mice. Privileged H-2Kb restriction to the response is not due to immunodominance or epistatic effect but due to Ir gene function of H-2Kb itself.

Previous study demonstrated that anti-H-43a cytotoxic T lymphocyte (CTL) response of H-43b CWB (H-2b) stain carrying non-major histocompatability complex (MHC) genes of C3H and F1 strains raised by crossing CWB with various H-43b strains was restricted exclusively by self H-2Kb (Kb). In the present study, newly produced C3W strain (H-2k, H-43b), which is H-43-congenic to C3H/HeN (H-2k, H-43a), was used as H-43b mice, and possibility of immunodominance of Kb was examined. No anti-H-43a CTL response could be induced in C3W strain and F1 strains raised by crossing C3W with other H-43b strains not carrying Kb. Thus, the possibility of immunodominance of Kb over the other MHC class I alleles could not be supported. We also examined possibility of epistatic effect of I region genes and non-MHC genes on the Kb restriction. (C3W x C57BL/6)F1(I-Ak/b) and (C3W x B6.CH-2bm12)F1(I-Ak/bm12)mice showed equally anti-H-43a CTL response restricted exclusively by self Kb, and (C3W x B10.MBR)F1(Ik/k) mice also showed anti-H-43a CTL response restricted solely by self Kb. Cold target competition experiments demonstrated that H-43b C57BL/10 or A.BY mice, which do not have non-MHC genes of C3H mounted anti-H-43a CTL response restricted solely by self Kb. Thus, no relation of I region genes or non-MHC genes to the Kb restriction was shown. All the results indicate that H-43b mouse strains, including F1, can not achieve anti-H-43a CTL response unless they carry Kb allele. Notably, (C3W x C57BL/6)F1 mice mounted self Kb-restricted anti-H-43a CTL response, whereas (C3W x B6.CH-2bm1)F1 mice carrying mutated Kb could not mount anti-H-43a CTL response at all. These findings indicate strongly that Kb itself is classical Ir gene of anti-H-43a CTL response and directs self Kb restriction of the response.

Animals↗
PubMed1989

Escherichia coli dnaT gene function is required for pBR322 plasmid replication but not for R1 plasmid replication.

Plasmid pBR322 was unable to replicate in a temperature-sensitive dnaT1 strain at a nonpermissive temperature, whereas a pBR322-derived plasmid carrying the wild-type dnaT+ gene was able to replicate under the same conditions. In contrast to pBR322, plasmid R1 could replicate in the dnaT1 strain at a nonpermissive temperature. In keeping with this finding, in vitro replication of plasmid R1 did not require DnaT protein.

DNA Replication↗
PubMed1987

Selective inhibition of interleukin 2 gene function following thymocyte antigen/major histocompatibility complex receptor crosslinking: possible thymic selection mechanism.

Considerable evidence now exists to support the notion that the 50-kDa sheep erythrocyte binding protein, T11, represents an essential cell surface component of a human T-cell-lineage activation pathway. Furthermore, it is known that the human T-cell antigen-major histocompatibility complex (MHC) receptor complex T3-Ti is capable of regulating cell growth mediated by the T11 structure. Here we show that, within the T3+ thymocyte compartment, T3-Ti crosslinking rapidly inhibits T11-initiated interleukin 2 (IL-2) gene transcription and translation. This inhibition is restricted to the IL-2 gene (IL2) as transcription of both the IL-2 receptor gene (IL2R) and the Ti beta-chain gene (TCRB) are not affected (human gene designations are in parentheses). Perhaps more importantly, T3-Ti-mediated IL-2 inhibition of this type is not operational in peripheral T lymphocytes. The results imply that the majority of T3+ thymocytes are functionally distinct from peripheral T lymphocytes despite their T3+ phenotype and may possess a unique endogenous regulatory component for suppressing IL-2 gene activity. Moreover, since IL-2 is likely rate-limiting for growth within the thymus, the findings provide one plausible mechanism for thymic selection--namely, T3-Ti crosslinking of thymocytes upon interaction with self-major histocompatibility complex inhibits clonal expansion of high-affinity autoreactive cells.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1975

chlD gene function in molybdate activation of nitrate reductase.

chlD mutants of Escherichia coli lack active nitrate reductase but form normal levels of this enzyme when the medium is supplemented with 10-3 M molybdate. When chlD mutants were grown in unsupplemented medium and then incubated with molybdate in the presence of chloramphenicol, they formed about 5% the normal level of nitrate reductase. Some chlD mutants or the wild type grown in medium supplemented with tungstate accumulated an inactive protein which was electrophoretically identical to active nitrate reductase. Addition of molybdate to those cells in the presence of chloramphenicol resulted in the formation of fully induced levels of nitrate reductase. Two chlD mutants, including a deletion mutant, failed to accumulate the inactive protein and to form active enzyme under the same conditions. Insertion of 99-Mo into the enzyme protein paralleled activation; 185-W could not be demonstrated to be associated with the accumulated inactive protein. The rates of activation of nitrate reductase at varying molybdate concentrations indicated that the chlD gene product facilitates the activation of nitrate reductase at concentrations of molybdate found in normal growth media. At high concentrations, molybdate circumvented this function in chlD mutants and appeared to activate nitrate reductase by a mass action process. We conclude that the chlD gene plays two distinguishable roles in the formation of nitrate reductase in E. coli. It is involved in the accumulation of fully induced levels of the nitrate reductase protein in the cell membrane and it facilitates the insertion of molybdenum to form the active enzyme.

Cell-Free System↗