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Biomedical subjects

J Carbon

Publications and source records attributed to J Carbon.

At least 91 records · Page 5Linked to original sources
PubMed1976

Construction and analysis of viable deletion mutants of simian virus 40.

Viable mutants of simian virus 40 (SV40), with deletions ranging in size from 15 to 200 base pairs, have been obtained by infecting CV-1P cells with circularly permuted linear SV40 DNA. The linear DNA was produced by cleavage of closed circular DNA with DNase I in the presence of Mn2+, followed, in some cases, by mild digestion with lambda 5'-exonuclease. The SV40 map location and the size of each deletion were determined by using the S1 nuclease mapping procedure (Shenk et al., 1975) and the change in size of fragments produced by Hind II + III endonuclease cleavage. Deletions in at least three regions of the SV40 chromosome have slight or no effect on the rate or yield of viral multiplication and on vira-induced cellular transformation. These regions are located at the following coordinates on the SV40 physical map: 0.17 to 0.18; 0.54 to 0.59; and 0.68 to 0.74.

Cell Line↗
PubMed1975

Nucleotide sequence studies of normal and genetically altered glycine transfer ribonucleic acids from Escherichia coli.

The total nucleotide sequence of tRNAGGA/G -Gly2 from Escherichia coli is pG-C-G-G-G-C-A-U-C-G-U-A-U-A-A-U-G-G-C-U-A-U-U-A-C-C-U-C-A-G-C-C-U-N-C-C-A-A-G-C-U-G-A-U-G-A-U-G-C-G-G-G-T-psi-C-G-A-U-U-C-C-C-G-C-U-G-C-C-C-G-C-U-C-C-AOH, where T- at position 53 is ribothymidylic acid, and psi- at position 54 is pseudouridylic acid; N- at position 36 is an unidentified derivative of uridylic acid, and is present in modified form in a portion of tRNAGGA/G -Gly 2 molecules isolated from E. coli cells. The missense suppressor mutation, glyTsuA36(HA), results in a C yields U base substitution at the 3' end of the anticodon of tRNAGGA/G -Gly 2 (nucleotide position 38). A secondary effect of this base substitution is the modification of the A residue directly adjacent to the 3' end of the anticodon of tRNAsuA36(HA), -Gly 2 suggesting that the enzymes responsible for this modification recognize the anticodon sequences of prospective tRNA substrates. The creation of a missense-suppressing tRNA, tRNAsuA36(HA), -Gly 2 by an alteration of the anticodon sequence of tRNAGGA/G -Gly 2 is analogous to mechanisms whereby other suppressor tRNAs have arisen. The high degree of nucleotide sequence homology between the amino acid acceptor stems and anticodon regions of four glycine isoaccepting tRNAs specified by E. coli and bacteriophage T4 suggests that these regions may be recognized by the glycyl-tRNA synthetase; the involvement of the anticodon region in the synthetase recognition process is supported by the greatly decreased rate of aminoacylation of tRNAsuA36(HA) -Gly 2.

Anticodon↗
PubMed1975

The nucleotide sequence of a precursor to the glycine- and threonine-specific transfer ribonucleic acids of Escherichia coli.

The primary nucleotide sequence of an Escherichia coli tRNA precursor molecule has been determined. This precursor RNA, specified by the transducing phage lambdah80dglyTsuA36 thrT tyrT, accumulates in a mutant strain temperature-sensitive for RNase P activity. The 170-nucleotide precursor RNA is processed by E. coli extracts to form mature tRNA Gly 2 suA36 and tRNA Thr ACU/C. The sequence of the precursor is pG-U-U-C-C-A-G-G-A-U-G-C-G-G-G-C-A-U-C-G-U-A-U-A-A-U-G-G-C-U-A-U-U-A-C-C-U-C-A-G-C-C-U-N-C-U-A-A-G-C-U-G-A-U-G-A-U-G-C-G-G-G-T-psi-C-G-A-U-U-C-C-C-G-C-U-G-C-C-C-G-C-U-C-C-A-A-G-A-U-G-U-G-C-U-G-A-U-A-U-A-G-C-U-C-A-G-D-D-G-G-D-A-G-A-G-C-G-C-A-C-C-C-U-U-G-G-U-mt6A-A-G-G-G-U-G-A-G-m7G-U-C-G-G-C-A-G-T-psi-C-G-A-A-U-C-U-G-C-C-U-A-U-C-A-G-C-A-C-C-A-C-U-UOH(tRNA sequences are italicized). It contains the entire primary nucleotide sequences of tRNA Gly2 suA36 and tRNA Thr ACU/C, including the common 3'-terminal sequence, CCA. Nineteen additional nucleotides are present, with 10 at the 5' end, 3 at the 3' end, and the remaining 6 in the inter-tRNA spacer region. RNase P cleaves the precursor specifically at the 5' ends of the mature tRNA sequences.

Autoradiography↗
PubMed1975

Biochemical construction and selection of hybrid plasmids containing specific segments of the Escherichia coli genome.

Using a poly(dA-dT) "connector" method, a population of annealed hybrid circular DNAs was constructed in vitro; each hybrid DNA circle containing one full-length molecule of poly(dT)-tailed DNA from E1 colicinogenic factor (Col E1) fragmented by EcoRI endonuclease annealed to any one of a collection of poly(dA)-tailed linear DNA fragments of the entire E. coli genome. This annealed, but unligated, hybrid DNA was used to transform several different auxotrophic mutants of E. coli, and by direct selection, bacterial clones were isolated which contained specific hybrid plasmids. In this manner, bacterial strains containing Col E1 hybrid plasmids carrying the entire tryptophan operon or the arabinsoe and leucine operons were isolated. The methods described should allow the molecular cloning of any portion of the E. coli genome by selection from a pool of DNA molecules containing at least several hundred different hybrids representing the entire bacterial genome.

Arabinose↗
PubMed1975

Biochemical procedure for production of small deletions in simian virus 40 DNA.

A simple biochemical procedure for producing small deletions (15 to 50 base pairs) at virtually any location in simian virus 40 DNA has been developed. The steps involved are: cleavage of the closed-circular DNA to produce a linear structure followed by 5'-exonuclease digestion to expose a short single-stranded segment at each 3' end of the molecule. Mutants containing deletions at the site of the cleavage are obtained by infecting permissive monkey kidney cells with the exonuclease-treated DNA in the presence or absence of a helper DNA (depending upon whether or not the site of cleavage and therefore the deletion occurred in a gene required for vegetative multiplication). In this paper viable mutants with deletions at the HpaII endonuclease cleavage site (0.735 map position) and defective trans-complementable mutants with deletions at the EcoRI endonuclease cleavage site (0/1.0 map position) were isolated.

Coliphages↗
PubMed1975

Multiple gene loci for a single species of glycine transfer ribonucleic acid.

The study of suppressors of tryptophan synthase A protein missense mutations in Escherichia coli has led to the establishment of two nonadjacent genetic loci (gly V and gly W) specifying identical nucleotide sequences for a single isoaccepting species of glycine transfer ribonucleic acid (tRNA GLY 3 GGU/C). In one case, suppression of the missense mutation trpA78 was due to a mutation in a structural gene (gly W) for tRNA Gly 3 GGU/C. This mutation resulted in a base change in the anticodon and modification of an A residue adjacent to the 3' side of the anticodon, leading to the production of a tRNA Gly 3 UGU/C species. The resulting glyW51 (SU UGU/C) allele was mapped by interrupted mating and was located at approximately 37 min on the Escherichia coli genetic map. Other suppressor mutations affecting the primary sequence of tRNA Gly GGU/C and giving rise to the Ins and SU+A58 phenotypes were positioned at 86 min (glyV). Several independently arising missense suppressor mutations resulting in the SU+A78 phenotypes were isolated and mapped at these two genetic loci (glyV and glyW). The ratio of appearance of suppressor mutations at glyV and glyW suggests that there are three of four tRNAGly3 GGU/C structural gene copies at the glyV locus to one copy at the glyW locus. Structural genes for tRNA ly isoacceptors are now known at four distinct locations on the Escherichia coli chromosome: glyT (77 MIN), TRNA Gly 2 GGA/G; gly U (55 min), tRNAGly-1 minus; and gly V (86 MIN) AND GLYW (37 min), tRNAGly 3 GGU/C.

Alleles↗
PubMed1973

Three adjacent transfer RNA genes in Escherichia coli.

A defective varphi80 transducing phage has been isolated that carries a small section of the E. coli chromosome from the region near argH (77 min). This phage contains three E. coli tRNA genes, termed glyTsu(+) (36), tyrT, and thrT. These genes specify the structures of tRNA(2) (Gly) (su(+) (36)) tRNA(2) (Tyr), and tRNA(3) (Thr), respectively. Induction of a single lysogen bearing this phage brings about selective synthesis and amplification of only these three tRNAs.

Amino Acids↗