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J U Ericson

Publications and source records attributed to J U Ericson.

7 recordsLinked to original sources
PubMed1996

Mutation in the structural gene for release factor 1 (RF-1) of Salmonella typhimurium inhibits cell division.

A temperature-sensitive mutant of Salmonella typhimurium LT2 was isolated. At the nonpermissive temperature cell division stopped and multinucleated filaments were formed. DNA, RNA, or protein synthesis was not affected until after about two generations. Different physiological conditions, such as anaerobiosis and different growth media, suppress the division deficiency at high temperatures. Certain mutations causing a reduced polypeptide chain elongation rate also suppress the division deficiency. The mutation is recessive and shown to be in the structural gene for release factor I (prfA). DNA sequencing of both the wild-type (prfA+) and mutant (prfA101) allele revealed a GC-to-AT transition in codon 168. Like other known prfA mutants, prfA101 can suppress amber mutations. The division defect in the prfA101 mutant strain could not be suppressed by overexpression of the ftsQAZ operon. Moreover, at the nonpermissive temperature the mutant shows a normal heat shock and SOS response and has a normal ppGpp level. We conclude that the prfA101-mediated defect in cell division is not directed through any of these metabolic pathways, which are all known to affect cell division. We speculate that the altered release factor I induces aberrant synthesis of an unidentified protein(s) involved in the elaborate process of septation.

Aldehyde Oxidoreductases↗
PubMed1993

Genomic sequence and embryonic expression of the zebrafish homeobox gene hox-3.4.

We have analyzed the genomic DNA sequence and embryonic expression pattern of the zebrafish hox-3.4 gene. Two exons, encoding a protein with a total size of 232 amino acids, were identified within a 3.5 kbp genomic region. Besides the homeodomain, which is identical to that of the human HOX3D and mouse Hox-3.4 genes, the first 58 residues of the N-terminal domain in the predicted Hox-3.4 protein share 48% sequence identity with the gene product of the human cognate. Some of the N-terminal sequence elements are also conserved relative to the two other members of the Hox-1.3/Hox-2.1/Hox-3.4 paralogy group. In addition, the paralogous genes share a significant degree of sequence identity in non-coding regions. This conservation is particularly evident in the promoter regions of the cognates hox-3.4, Hox-3.4, and HOX3D, where a 180 bp TATA-box-containing element with a 60% identity is located. This is in agreement with the previous finding that the HOX3D promoter region contains response elements for other Hox proteins and retinoids. Also with respect to embryonic expression, the zebrafish hox-3.4 gene is very similar to its mammalian counterparts. Within the central nervous system of 16, 24, and 48 h embryos, hox-3.4 transcripts were detected throughout most of the spinal cord from a boundary at the posterior end of the hindbrain. In 16 h embryos the hox-3.4 gene is also active within a restricted region of the tailbud.

Amino Acid Sequence↗
PubMed1991

tRNA anticodons with the modified nucleoside 2-methylthio-N6-(4-hydroxyisopentenyl)adenosine distinguish between bases 3' of the codon.

The modified nucleoside 2-methylthio-N6-(4-hydroxyisopentenyl)adenosine (ms2io6A) is present immediately to the 3' side of the anticodon (position 37) in tRNAs that read codons starting with uridine and hence include amber (UAG) suppressor tRNAs. We have used strains of Salmonella typhimurium that differ only in their ability to synthesize ms2io6A in order to determine specifically how this modified nucleoside influences the efficiency of amber suppression in two codon contexts differing by only which base is 3' of the codon. The results show that the presence of the modified nucleoside ms2io6A not only improves the efficiency of the suppressor tRNAs but also allows them to distinguish between at least two bases 3' of the codon. Thus, the presence of ms2io6A reduces the intrinsic codon context sensitivity of the tRNA and specifically counteracts an unfavourable nucleotide on the 3' side of the codon. The possible codon-anticodon interactions responsible for this effect are discussed.

Anticodon↗
PubMed1991

Zebrafish pax[zf-a]: a paired box-containing gene expressed in the neural tube.

Murine and human sequences homologous to the paired box of the Drosophila segmentation gene paired have been reported previously. Here we describe a zebrafish (Brachydanio rerio) paired box-containing clone, pax[zf-a], which is clearly distinct from reported vertebrate Pax genes. The putative protein encoded by pax[zf-a] contains a paired box and a paired-type homeobox separated by a glycine-rich, acidic linker and a carboxy-terminal end which is remarkably rich in serine, threonine and proline residues. By in situ hybridization to embryonic tissue sections and whole mount embryos, pax[zf-a] transcripts were found within restricted regions of the central nervous system and the eye. In contrast to the murine Pax genes recently characterized, pax[zf-a] is not expressed in the segmented mesoderm. At the 17 h stage, pax[zf-a] expression is detected in a defined area of the diencephalon which circumscribes the presumptive thalamus. This suggests an involvement of pax[zf-a] in pattern formation in the rostral brain. The pax[zf-a] gene is also expressed throughout the hindbrain and spinal cord. This hybridization signal is restricted to a longitudinal column which includes the basal plate. Later in development, at 36 h post-fertilization, pax[zf-a] transcripts are no longer restricted to a specific region of the diencephalon, but are distributed over the entire developing brain.

Amino Acid Sequence↗
PubMed1990

Role of tRNA modification in translational fidelity.

In transfer RNA many different modified nucleosides are found, especially in the anticodon region. In this region, pseudouridine (psi) is found in positions 38, 39 or 40 in a subset of tRNA species, 2-methylthio-6-hydroxyisopentenyladenosine (ms2io6A) is found in position 37 in tRNAs that read codons starting with U and 1-methylguanosine (m1G) is found in position 37 in tRNAs reading codons of the UCCNG type. We have used the mutants hisT, miaA and miaB and trmD, which are deficient in the biosynthesis of psi, ms2io6A, and m1G, respectively, to study the functional aspects of the respective modified nucleosides. We have shown: (1) Presence of psi improved the cellular growth rate, the polypeptide step-time, and the efficiency of an amber suppressor, but did not appreciably sense the codon context. (2) Presence of ms2io6A improved the cellular growth rate, the polypeptide step-time and the efficiency of several amber suppressor tRNAs. It also had a profound effect on the codon context sensitivity of the tRNA. (3) Presence of m1G improved the cellular growth rate and the polypeptide steptime and also prevented the tRNA from shifting the reading frame. Thus, these three modified nucleosides present in the anticodon region have apparently different functions.

Anticodon↗
PubMed1986

Pleiotropic effects induced by modification deficiency next to the anticodon of tRNA from Salmonella typhimurium LT2.

A strain of Salmonella typhimurium LT2 was isolated, which harbors a mutation acting as an antisuppressor toward an amber suppressor derivative, supF30, of tRNATyr1. The mutant is deficient in cis-2-methylthioribosylzeatin[N6-(4-hydroxyisopentenyl)-2-me thylthioadenosine, ms2io6A], which is a modification normally present next to the anticodon (position 37) in tRNA reading codons starting with uridine. The gene miaA, defective in the mutant, is located close to and counterclockwise of the purA gene at 96 min on the chromosomal map of S. typhimurium with the gene order mutL miaA purA. Growth rate of the mutant was reduced 20 to 50%, and the effect was more pronounced in media supporting fast growth. Translational chain elongation rate at 37 degrees C was reduced from 16 amino acids per s in the wild-type cell to 11 amino acids per s in the miaA1 mutant in the four different growth media tested. The cellular yield in limiting glucose, glycerol, or succinate medium was reduced for the miaAI mutant compared with wild-type cells, with 49, 41, and 57% reductions, respectively. The miaAI mutation renders the cell more sensitive or resistant toward several amino acid analogs, suggesting that the deficiency in ms2io6A influences the regulation of several amino acid biosynthetic operons. We suggest that tRNAPhe, lacking ms2io6A, translates a UUU codon in the early histidine leader sequence with lowered efficiency, leading to repression of the his operon.

Anticodon↗