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At least 307 records · Page 17Linked to original sources
PubMed1986

Synthesis and maturation of recombinant human tumor necrosis factor in eukaryotic systems.

The biosynthesis of human tumor necrosis factor (hTNF) was studied. The amino-terminal extension of the hTNF precursor (26 kDa polypeptide) was not cleaved off in a cell-free system supplemented with dog pancreas microsomes. Correct maturation of pre-hTNF was nevertheless not restricted to the macrophage system: in the medium of a TNF-producing, transformed CHO cell line, a (weak) approximately 20 kDa, an approximately 18.5 kDa (doublet) and a 17 kDa TNF polypeptide, the latter corresponding to mature hTNF, were revealed by specific immunoprecipitation. Similar results were obtained with Xenopus laevis oocytes, injected with hTNF mRNA, except that the 20 kDa band was lacking. The results are discussed in relation to the secretion mechanism of hTNF.

Animals↗
PubMed1985

Three expressed sequences within the human beta-tubulin multigene family each define a distinct isotype.

This paper describes the isolation and complete sequence of a novel expressed human beta-tubulin gene (beta 2). The sequence is compared with that of two other expressed human beta-tubulin genes (M40 and 5 beta). All are encoded by four exons. Though the boundaries of each exon are absolutely conserved among the three genes, the intervening sequences differ considerably in size and sequence content. Two of the genes (M40 and 5 beta) contain one (M40) or ten (5 beta) members of the middle repetitive Alu family sequences within one of their intervening sequences. Comparison of the amino acid sequences encoded by each gene reveals a high level of homology overall, though there is significant divergence between the carboxy termini of two of the genes. The pattern of expression of each beta-tubulin gene has been studied in several different human cell lines using unique non-crosshybridizing probes derived from the 3' untranslated regions. Two of the genes, M40 and beta 2, are expressed at varying levels in all of the cell lines examined, though the level of expression of one of these genes parallels the other in most cases. The third gene, 5 beta, is detectably expressed only in cells of neural origin. Thus, distinct human beta-tubulin isotypes are encoded by genes whose exon size and number has been conserved evolutionarily, but whose pattern of expression may be regulated either co-ordinately or uniquely. Of the approximately 15 sequences contained in the human beta-tubulin multigene family, nine have now been sequenced fully. The overall composition of the multigene family and the evolutionary relationships among its various members are discussed.

Amino Acid Sequence↗
PubMed1988

Transcriptional activation of bacteriophage T4 middle promoters by the motA protein.

Transcriptional activation of middle genes in bacteriophage T4 requires the phage-encoded motA protein. Many middle genes are involved in deoxyribonucleotide biosynthesis and phage DNA replication. In the absence of motA, the gene products that are required for DNA synthesis are transcribed from other, upstream promoters. Using primer extension sequencing on RNA templates isolated from T4 motA+ and motA- infected cells, we have characterized 14 motA-dependent transcripts. The T4 middle promoters have a consensus sequence of nine base-pairs, (a/t)(a/t)TGCTT(t/c)A, spaced 11 to 13 nucleotides away from the Escherichia coli--10 consensus sequence, TAnnnT. The motA protein also can act as a transcriptional repressor for at least one early gene. Furthermore, the phage-encoded motA protein can activate in trans a middle promoter resident on a plasmid.

Base Sequence↗
PubMed1984

The nucleotide sequence of the Akv murine leukemia virus genome.

The nucleotide sequence of an infectious molecular clone of the Akv murine leukemia virus has been determined by the dideoxy chain termination method after subcloning in bacteriophage M13 vectors. The sequence predicts an RNA genome of 8371 nucleotides containing three large open reading frames corresponding to the gag, pol, and env genes. Signal sequences for transcription, splicing, and translation have been identified. The positions of 95 major RNase T1 resistant oligonucleotides of the Akv RNA genome have been located.

AKR murine leukemia virus↗
PubMed1985

Nucleotide sequence and structure of integrated bovine leukemia virus long terminal repeats.

Bovine leukemia virus (BLV) proviruses, harbored by the productively infected fetal lamb kidney (FLK-BLV) cell line, were cloned in bacteriophage lambda L47. The nucleotide sequence of the proviral long terminal repeats (LTR) with flanking cell and virus DNA have been determined. The BLV LTR is 531 bp in length and is bounded by the dinucleotides 5'-TG...CA-3', which are part of a 3-bp inverted repeat. The integrated provirus is flanked by 6-bp direct repeats of cellular DNA. A tRNApro primer binding site is present starting 2 bp downstream of the 5' LTR. In addition to sequencing integrated proviral DNA clones, the nucleotide sequence of a cDNA clone, representing the 3' end of genomic viral RNA, was determined; thus revealing the RNA polyadenylation site and R:U5 boundary within the LTR. Unlike most other retroviruses, a consensus polyadenylation signal, "AATAAA," is not located proximal to the BLV polyadenylation site. The RNA initiation site, defining the U3:R boundary, was located in the BLV LTR by S1 nuclease mapping. This site is approximately 25 bp downstream of an A + T-rich region which probably encompasses a Goldberg-Hogness ("TATAA") box and about 90 bp downstream of a potential "CCAAT" box. The BLV LTR possesses a U3 region of 204 bp, an unusually long R region of 241 bp, and a U5 region of 86 bp.

Base Sequence↗
PubMed1990

Infectious transcripts and nucleotide sequence of cloned cDNA of the potexvirus white clover mosaic virus.

The complete nucleotide sequence of white clover mosaic virus (WCIMV) strain O has been determined and compared to the WCIMV strain M sequence. The two virus strains show 12% divergence at the nucleotide level and 3% divergence at the amino acid level (open reading frames 1 to 5). Two open reading frames, 10 and 21 kDa, identified in the strain M sequence were not found in the strain O sequence. High levels of infectious RNA transcripts were produced from a full-length cDNA clone of strain O constructed downstream of the SP6 RNA polymerase promoter (greater than 2 micrograms RNA/micrograms template DNA). Symptoms characteristic of WCIMV developed when host plants were inoculated with SP6 RNA transcripts. The specific infectivity of transcript RNA produced in the presence of m7GpppG was similar to that of virion RNA. The SP6 transcripts lacked 5' nonviral nucleotides, but contained 6, 14, or 198 3' nonviral nucleotides (derived from the pUC19 vector). Transcripts were infectious without m7GpppG, or with long nonviral 3' nucleotide stretches. Progeny virus RNA from infections initiated with transcripts containing 198 nonviral 3' nucleotides did not maintain these sequences.

Base Sequence↗
PubMed1979

The nucleotide sequence of the initiation and termination sites for ribosomal RNA transcription in X. laevis.

In this study, we have located the sites of transcription initiation and termination on a cloned fragment of ribosomal DNA from X. laevis, and have sequenced the surrounding nucleotides. As reported previously (Reeder, Sollner-Webb and Wahn, 1977), about 25% of the 40S rRNA precursor molecules isolated from oocytes have polyphosphate 5' termini and are therefore presumed to represent primary transcripts. These ends hybridize specifically to the 221 bp DNA fragment and removed the overhanging DNA region with S1 nuclease. In the other, we hybridized 40S RNA to a 221 bp fragment of ribosomal DNA. The nucleotides encoding the 5' end of the 40S RNA were located more precisely by two methods. In one, we hybridized 40S RNA to the 221 bp DNA fragment and removed the overhanging DNA region with S1 nuclease. In the other, we hybridized 40S RNA to a smaller DNA fragment and extended the recessed 3' terminus of the DNA using reverse transcriptase. The resultant DNA fragments were sized on sequencing gels. Both determinations map the 5' end of 40S RNA at the same site in the rDNA, about 2250 bp upstream from the Eco RI site in the 18S rRNA coding sequence. At this site we find a DNA sequence beginning AGGGGAAGAC.... which agrees with partial sequence data from the 5' end of polyphosphorylated and bulk 40S rRNA. Features of this region of the ribosomal DNA will be discussed in this paper. A 227 nucleotide region surrounding the initiation site was also sequenced from an independently derived clone and found to differ in only one nucleotide. In addition, a sequence is found about 1100 nucleotides upstream from the 5' end of the gene that has 90% homology to the sequence from nucleotides minus 125 to +4 in the initiation region. At the termination region, X. laevis ribosomal DNA has a single recognition site for the restriction enzyme Hind III in each repeating unit. Using the S1 nuclease technique, the 3' termini of both the 40S precursor and mature 28S rRNA are seen to map within this recognition sequence. The sequence surrounding the Hind III site has striking homology to termination sites recognized by other RNA polymerase classes. Sequences with similar features are also found upstream from the initiation site.

Animals↗