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J L Bos

Publications and source records attributed to J L Bos.

At least 163 records · Page 9Linked to original sources
PubMed1984

The first exon of region E1a genes of adenoviruses 5 and 12 encodes a separate functional protein domain.

The transforming E1 regions of human adenoviruses Ad5 and Ad12 differ from each other in the frequency by which they can transform primary baby rat kidney cells, and in their ability to modulate expression of class I major histocompatibility (MHC) genes. We have investigated whether these two properties, which are determined by region E1a, can be assigned to one of the two protein segments encoded by the E1a exons. To that end, we have constructed chimaeric E1a regions, in which the 5' E1a exon of Ad5 was linked to the 3' E1a exon of Ad12, and vice versa. It was found that, although there is only a limited degree of homology between Ad5 and Ad12 E1a (approximately 40% at the protein level), the hybrid E1a products are functional in transformation. Furthermore, both the frequency of transformation and the modulation of class I MHC gene expression appeared to be determined by the first E1a exon. These results indicate that the first E1a exon encodes a separate functional domain in the E1a proteins.

Adenoviruses, Human↗
PubMed1983

Characterization of satellite DNA in Trypanosoma brucei and Trypanosoma cruzi.

We have determined the properties of the simple-sequence satellite DNAs from two protozoa, Trypanosoma brucei and Trypanosoma cruzi. The T. brucei satellite DNA contains 29 mol% guanine plus cytosine and is made up of long tandem arrays of a 177 base-pair repeat. Sequence heterogeneity in these repeats is limited and restricted to certain positions as shown by sequence analysis, restriction enzyme digestion and two-dimensional analysis of nucleotides bordering the AluI and HhaI recognition sites in the repeat. The repeat contains two copies of a 19 base-pair sequence differing by a single base-pair substitution and several additional copies of part of this sequence. Sequence variants of the repeat are clustered in the DNA. Satellite DNA is not detectably linked to other DNA and no transcripts of this DNA are found in T. brucei. The T. cruzi satellite DNA repeat is 196 base-pairs long and contains 53 mol% guanine plus cytosine. Direct repetitions longer than eight base-pairs were not observed in the nucleotide sequence of this repeat. The nucleotide sequences of the satellites of T. brucei and T. cruzi are not related. In cell fractionation experiments, the T. brucei and T. cruzi satellite DNAs were recovered from the nuclear fraction. Micrococcal nuclease digestion of nuclear fractions yielded 193 and 197 base-pair nucleosomal oligomers in T. brucei and T. cruzi, respectively; these oligomers contained satellite DNA but not the extranuclear kinetoplast DNA. The 193 base-pair nucleosomal repeat of T. brucei is significantly different from the 177 base-pair satellite repeat. Satellite and nucleosomal repeats are, therefore, not in phase in T. brucei. These satellite DNAs are the first to be observed in protozoa, and we conclude that their properties are similar to those of satellites from animals or plants.

Animals↗
PubMed1983

The E1b promoter of Ad12 in mouse L tk- cells is activated by adenovirus region E1a.

We have investigated the effect of the E1a region of adenovirus on the expression of the E1b transcriptional unit in mouse L tk- cells. To that end we have fused the promoter region of the E1b gene of Ad12 to the coding sequence of the thymidine kinase gene of herpes simplex virus type 1. We found that expression of this fusion gene is completely dependent on the presence of the E1a region. Sequences involved in this regulation were mapped between positions -135 and +11 from the E1b cap site. In addition, we found that the largest E1a protein is essential in this regulation process.

Adenovirus E1A Proteins↗
PubMed1983

Deletion mutants of region E1a of AD12 E1 plasmids: effect on oncogenic transformation.

Plasmids containing the E1 region of Ad12 DNA can transform certain rodent cells into oncogenic cells. To study the role of the E1a subregion in the process of oncogenic transformation, Ad12 region E1 mutants carrying deletions in the E1a region were constructed. Deletion mutants pR7 and pR8 affect only the 13 S mRNA species encoded by region E1a, whereas deletion mutants pR11 and pR15 damage both the 12 S and 13 S E1a mRNA. All four mutants have lost their capacity to transform primary cultures of baby rat kidney cells, indicating that the E1a gene product encoded by 13 S mRNA is essential for transformation. It was further found that the mutated E1a regions of both pR7 and pR11 can induce expression of region E1b, which implies that the transformation deficiency of these mutants is not due to the inability to activate E1b expression. Surprisingly, the transforming capacity of pR7 and pR11 is restored when these mutant E1 regions are covalently coupled to the SV40 "enhancer" region. Cells transformed by these hybrids plasmids, however, were not tumorigenic in nude mice.

Adenoviruses, Human↗
PubMed1983

Role of adenovirus types 5 and 12 early region 1b tumor antigens in oncogenic transformation.

Recently we have reported that the difference in oncogenic potential between adenovirus type 5 (Ad5)-and Ad12-transformed cells in athymic nude mice is specified by early region 1b. In order to determine which of the two early region 1b (E1b) tumor antigens is responsible for the observed difference in oncogenicity we have constructed two Ad5/Ad12 hybrid plasmids: one allowing expression of the Ad5 19kD and Ad12 54kD E1b proteins, the other of the Ad5 58kD plus Ad12 19kD E1b polypeptides. Both hybrid plasmids contain the intact E1a regions of both serotypes. The chimeric plasmids were used to transform primary cultures of baby rat kidney cells and the resulting transformed cells were tested for oncogenicity in athymic nude mice. It was found that the degree of oncogenicity is determined by the identity of the large E1b tumor antigen. Studies with cells transformed by an Ad12 region E1 plasmid in which the gene coding for the 19kD tumor antigen was mutated showed that expression of this protein is nevertheless required for manifestations of the oncogenic phenotype of the transformed cell.

Adenoviruses, Human↗
PubMed1981

Fine structure of the 21S ribosomal RNA region on yeast mitochondrial DNA. IV. Characterization of the omega neutral allele.

The omega locus controls the polarity of recombination and transmission of genetic markers in the 21S ribosomal RNA region in yeast mtDNA. Polarity is observed in crosses between omega+ and omega- strains. These two strains differ by the presence of an intervening sequence in the 21S ribosomal RNA gene of omega+ strains. Mutations of the omega- allele, omega neutral (omegan), can eliminate the polarity effect. We have made DNA:RNA hybrids containing ribosomal RNA from an omegan strain and mtDNA from Saccharomyces carlsbergensis (identical to omega- in the nucleotide sequence of the omega region). These hybrids contain no mismatch at the omega region detectable by digestion with S1 nuclease. We conclude that omegan differs from omega- only in a point mutation or analogous small alteration and that the omegan mutation can result either in a Cr phenotype (omeganCr) or in the phenotypic suppression of pre-existing Cr mutations (omegenCs). All results can be explained by a model which postulates interaction in the ribosome between the Cr and omegan regions of the ribosomal RNA and interference of the omegan mutation with splicing of the precursor ribosomal RNA in omega+ strains. The mechanism of omega-directed polarity is discussed.

Alleles↗
PubMed1981

The 2.2 kb E1b mRNA of human Ad12 and Ad5 codes for two tumor antigens starting at different AUG triplets.

By nucleotide sequence analysis and S1 nuclease mapping we have determined the structural organization of early region E1b of Ad12. We have also revised the nucleotide sequence of the E1b region of Ad5. Both regions have an identical structural organization and show considerable homology at the nucleotide level. The major tumor antigens (Ad12, 19 and 54 kilodaltons [kd]); Ad5, 21 and 55 kd) are encoded in two overlapping reading frames. A single mRNA of 2.2 kilobases codes for both these proteins, depending on which AUG triplet serves as the start codon: the 19-21 kd protein initiates at the 5'-promximal AUG; the 54-55 kd protein initiates at the second AUG in another reading frame. Peptide mapping shows that the small and large tumor antigens do not share common tryptic peptides, in accordance with the nucleic acid sequence data. In addition, the 19-21 kd protein can also by synthesized from a one kilobase mRNA. Finally, the gene for the Ad12 analog of protein IX is characterized.

Adenoviruses, Human↗
PubMed1980

Splice point sequence and transcripts of the intervening sequence in the mitochondrial 21S ribosomal RNA gene of yeast.

By S1 nuclease mapping we have located the intervening sequence in the large ribosomal RNA gene of Saccharomyces cerevisiae omega+ strains 570 bp from the 3' end of the rRNA gene. No intervening sequence was detected at this position in S. carlsbergensis, but the sequences of the mature 21S rRNAs of these two strains appear to be identical in this region. By comparing the DNA sequence of the region of the intervening sequence in an omega+ strain with the corresponding sequence in S. carlsbergensis, we have determined the splice points of the 21S rRNA gene. These sequences show no homology with splice points in nuclear and viral genes or with the splice points in the chloroplast 23S rRNA gene of Chlamydomonas. The external borders of the splice points have a complementary sequence in the intervening sequence. The largest transcript hybridizing with the probe of the intervening sequence has a size corresponding to that expected for an rRNA precursor still containing the intervening sequence; the smallest transcript corresponds in size to the intervening sequence itself.

Base Sequence↗
PubMed1979

Nucleotide sequence of the mitochondrial structural genes for cysteine-tRNA and histidine-tRNA of yeast.

We have determined the nucleotide sequence of a segment of Saccharomyces cerevisiae mtDNA that contains the structural genes for a cysteine-tRNA and a histidine-tRNA. The genes are approximately 85 bp apart, they do not contain intervening sequences or sequences coding for the 3'-CCA terminus and they are surrounded by nearly pure AT segments. The tRNAs deduced are very AT-rich, 74 and 75 nucleotides long, respectively, and contain one or more unusual features not found in tRNAs from other sources.

Base Sequence↗
PubMed1979

Fine structure of the 21S ribosomal RNA region on yeast mitochondria DNA. I. Construction of the physical map and localization of the cistron for the 21S mitochondrial ribosomal RNA.

1. We have used restriction enzyme analysis of petite mtDNAs to construct a detailed physical map of the 21S region on the mtDNA of the Saccharomyces cerevisiae strain JS1-3D. The map covers a segment of about 20,000 bp, on which the recognition sites of the enzymes HapII, HindII, HindIII, Sa1I, XhoI and HhaI have been localized (22 sites in total). This map has been checked in various ways against the independently constructed overall physical map of the mtDNA of strain JS1-3D. In addition, we have constructed a physical map with a resolution of about 200 bp of a HapII fragment of 1850 bp long, which carries the loci omega, RIB-1 and probably RIB-2. 2. The 21S rRNA hybridizes with the five adjacent HindII + III fragments TD9, DT19, TD15, DT14 and TT1, which lie in that order on the physical map of the 21S region. Of these, the two non-adjacent fragments TD9 and DT14 show a much stronger hybridization with 21S rRNA than DT19, TD15, and TT1. 3. The fragment DD5 (= DT19 + TD15) and part of DT14 belong to a sequence of about 1000 bp, which is absent from Saccharomyces carlsbergensis mtDNA. Although DD5 and DT14 show (very weak, respectively stronger) hybridization with 21S rRNA, the 1000 bp insert probably does not code for the 21S rRNA: the 21S rRNA of S. carlsbergensis comigrates with the 21S rRNA of JS1-3D on polyacrylamide gels under denaturing conditions. 4. Fragment DT14 hybridizes with the HindII + III fragment TD9, which shows the strongest hybridization with 21S rRNA. The presence of these sequence homologies has hampered the precise mapping of the 21S rRNA cistron. Our results are compatible, however, with the hypothesis that the sequences, coding for 21S rRNA, are located on HindII + III fragments that are not adjacent on JS1-3D mtDNA, namely TD9, DT14 and TT1.

DNA Restriction Enzymes↗
PubMed1979

Nucleotide sequence of the mitochondrial structural gene for subunit 9 of yeast ATPase complex.

We have determined the nucleotide sequence of a segment of Saccharomyces mtDNA that contains the structural gene for one of the subunits (the dicyclohexylcarbodiimide-binding protein) of the mitochondrial ATPase complex. The sequence fits the known amino acid sequence of this protein with the exception of one amino acid. Codon usage is biased in favor of A + T-rich codons. On both sides of the gene, the nucleotide sequence contains less than 4% (mol/mol) G + C for at least 180 nucleotides; these A + T sequences show no evidence of internal repetition. The gene and all the A + T-rich sequence preceding the gene are present in a 12S RNA that is the major transcript of this segment of mtDNA. The nature of the sequences responsible for binding ribosomes to mitochondrial mRNA and for termination of RNA synthesis is considered.

Adenosine Triphosphatases↗
PubMed1978

A conserved and unique (AT)-rich segment in yeast mitochondrial DNA.

The mtDNA of the cytoplasmic petite mutant of yeast RD1A consists mainly of a perfect head-to-tail repetition of a known sequence of 66 consecutive AT and 2 GC base pairs. We have hybridized complementary RNA made on RD1A mtDNA with the mtDNAs of four different wild-type Saccharomyces strains that differ markedly in restriction fragmentation pattern. The tm's of the four heteroduplexes are identical to the tm of the homoduplex of RD1A mtDNA with complementary RNA of one repeat length. With all four wild-type mtDNAs this complementary RNA hybridizes mainly to a single restriction fragment of about 300 base pairs. This shows the conservation and individuality of at least one (AT)-rich segment in yeast mtDNA. The 300 base pair fragment has been mapped in the vicinity of the oxi-2 locus. The possible role of the (AT)-rich segment in the processing of the primary transcript of this region is discussed.

Adenine↗
PubMed1977

The repeating nucleotide sequence in the repetitive mitochondrial DNA from a "low-density" petite mutant of yeast.

The repeating nucleotide sequence of 68 base pairs in the mtDNA from an ethidium-induced cytoplasmic petite mutant of yeast has been determined. For sequence analysis specifically primed and terminated RNA copies, obtained by in vitro transcription of the separated strands, were use. The sequence consists of 66 consecutive AT base pairs flanked by two GC pairs and comprises nearly all of the mutant mitochondrial genome. The sequence, moreover, also represents the first part of wild-type mtDNA sequence so far.

Base Sequence↗
PubMedDate not supplied

p21ras: an oncoprotein functioning in growth factor-induced signal transduction.

p21ras is a small GTPase that functions as a molecular switch in intracellular signal transduction pathways activated by a large variety of growth factors. In 50% of colorectal tumours, one of the genes for p21ras is mutated resulting in a constitutive active protein. Recently, progress has been made in the elucidation of the signalling pathways in which p21ras is involved. After a ligand binds to growth factor receptors, in particular receptor tyrosine kinases, a guanine nucleotide exchange factor is activated, which results in p21ras in the GTP-bound form. This GTP-bound form of p21ras interacts with the protein kinase raf1 and induces the activation of a kinase cascade, resulting in various cellular responses. This kinase cascade is part of an integrated network of both positive and negative signalling events.

Animals↗
PubMedDate not supplied

Tumorigenicity of cells transformed by adenovirus type 12 by evasion of T-cell immunity.

Evidence is presented that cells transformed by adenovirus type 12 are oncogenic because they escape from T-cell immunity. This effect is brought about by reducing the expression of class I transplantation antigens and is a function of the protein translated from the 13S mRNA, transcribed from early region 1a. These findings establish a novel mechanism by which transformed cells can acquire an oncogenic phenotype.

Adenoviridae↗
PubMedDate not supplied

Amino-acid substitutions at codon 13 of the N-ras oncogene in human acute myeloid leukaemia.

DNAs from four out of five patients with acute myeloid leukaemia (AML) tested by an in vivo selection assay in nude mice using transfected mouse NIH 3T3 cells were found to contain an activated N-ras oncogene. Using a set of synthetic oligonucleotide probes, we have detected a mutation at codon 13 in all four genes. The same codon is mutated in an additional AML DNA that is positive in the focus-formation assay on 3T3 cells. DNA from the peripheral blood of one patient in remission does not contain a codon 13 mutation.

Amino Acid Sequence↗