Ethics and multicentre research projects.
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Ethics Committees↗
Biomedical subjects
R Horwitz
Publications and source records attributed to R Horwitz.
NusG, a new Escherichia coli elongation factor involved in transcriptional antitermination by the N protein of phage lambda.
We have reconstituted biologically relevant transcriptional antitermination in vitro by the phage lambda N protein. This required the isolation of NusG, a newly identified Escherichia coli transcription elongation factor. NusG is encoded by an E. coli gene, formerly called U and now called nusG, in which a mutation affects antitermination by N in vivo. Efficient antitermination by N in our reconstituted system depends on the bacterial proteins NusG, NusA, NusB, and ribosomal protein S10 (which functions without ribosomes in transcriptional antitermination). In reactions containing E. coli S100 extract, NusG is stoichiometrically bound to lambda N-modified transcription elongation complexes. We used RNA polymerase affinity chromatography to show that NusG binds to the core component of E. coli RNA polymerase. This binding is weak, and the stable association of NusG with lambda elongation complexes additionally requires at least N, NusA, and the boxA component of an N utilization site. In reactions containing bacterial S100 extract, NusG and NusB are also present in elongation complexes transcribing E. coli boxA-containing rDNA.
Amino Acid Sequence↗
Human histidyl-tRNA synthetase: recognition of amino acid signature regions in class 2a aminoacyl-tRNA synthetases.
We have determined the sequence of cDNA for the human histidyl-tRNA synthetase (HRS) in a hepatoma cell line and confirmed it in fetal myoblast and fibroblast cell lines. The newly determined sequence differs in 48 places, including insertions and deletions, from a previously published sequence. By sequence specific probing and by direct sequencing, we have established that only the newly determined sequence is present in genomic DNA and we have sequenced 500 hundred bases upstream of the translation start site. The predicted amino acid sequence now clearly demonstrates all three motifs recognized in class 2 aminoacyl-tRNA synthetases. Alignment of E. coli, yeast, and when available, mammalian predicted amino acid sequences for three of the four members of the class 2a subgroup (his, pro, ser, and thr) shows strong preservation of amino acid specific signature regions proximal to motif 2 and proximal to motif 3. These probably represent the active site binding regions for the proximal acceptor stem and for the amino acid. The first two exons of human HRS contain a 32 amino acid helical motif, first described in human QRS, a class 1 synthetase, which is found also in a yeast RNA polymerase, a rabbit termination factor, and both bovine and human WRS, suggesting that it may be an RNA binding motif.
Amino Acid Sequence↗
Isolation and characterization of Abelson murine leukemia virus-transformed mast cell lines from midgestation embryonic placenta.
Abelson murine leukemia virus was used to transform cells of the midgestation embryonic placenta. The frequency of transformed foci in semisolid agarose was highest when cells were isolated at 10 days of gestation and cell lines could be established in liquid culture. The continuous cell lines express characteristics of cultured mast cells, including surface antigens which are shared with lymphocytes and mononuclear phagocytes. These results imply a relationship between the transforming gene product and the mast cell growth factor interleukin 3.
Abelson murine leukemia virus↗
Genetic and molecular analysis of division control in yeast.
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Amino Acid Sequence↗
Intravenous cholangiography in childhood.
Intravenous cholangiography (IVC) was performed on 102 children aged between one and 13 years. Eighty of the patients who were non-icteric were divided into four groups and received contrast medium containing either 53, 75, 106 or 150 mg iodine/kg body weight by intravenous injection over ten minutes. Complete demonstration of the common bile duct (CBD) was achieved in 85% of patients and in a similar proportion of all age groups. There was some delay in opacification of the CBD in young children but this was not of practical significance. The two higher dosage regimen gave significantly better results than the two lower dosages (p less than 0.001) and this improvement was evident in the young and older age groups. Nausea and vomiting occurred as side effects in 6%. In eight patients in whom there was inadequate demonstration by the standard IVC, an infusion technique over 3--8 hours was carried out. This improved the demonstration in three children with diagnostic results in two.
Adolescent↗