PubMed · 7227508
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J Zähringer, R Kandolf, W Raum. 1981-01-26. Decrease of myocardial mRNA in adriamycin-treated rats.. https://doi.org/10.1016/0014-5793(81)80279-7
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
In the modified release factor 2 (RF2) programmed translational frameshift (with a sense codon replacing the wild-type in-frame UGA codon at the shift site), ribosomes shift +1 into the reading frame for an out-of-frame reporter fused to the frameshift sequence. Partitioning of ribosomes between the out-of-frame shift and in-frame reading depends on the codon at the shift site and on the levels of tRNA decoding the in-frame codon. Overexpression of a tRNA species cognate to the in-frame codon at the shift site significantly reduces the frequency of frame-shifting, presumably by facilitating in-frame reading, which would reduce production of the out-of-frame reporter. However, since overexpression of a tRNA increases levels of both charged and uncharged tRNA, it is possible that uncharged cognate tRNA might be able to reduce the frequency of the frameshift, by entering the A site on the ribosome. To test this, we manipulated charged and uncharged tRNA levels in vivo, using the tryptophan analog tryptophan hydroxamate, which increases the proportion of uncharged tRNA(Trp) by competing with cognate amino acid tryptophan for tryptophanyl-tRNA synthetase, thereby reducing protein synthesis. We report here that a slight but reproducible reduction in the relative frequency of the frameshift is observed when tryptophan hydroxamate is added to cells containing the modified RF2 shift with UGG (Trp codon) at the shift site. When tRNA(Trp) is overexpressed from another plasmid, the shift frequency drops three- to fourfold, as expected, however, this reduction is still seen in the presence of the analog. Thus, under conditions when most of the tRNA(Trp) is apparently uncharged, excess tRNA(Trp) still causes a significant reduction in the frameshift when UGG is at the shift site, providing evidence that uncharged cognate tRNA also can inhibit this frameshift.
The size distribution of aminoacyl-tRNA synthetase activity was investigated in cell extracts prepared from Saccharomyces cerevisiae. Bio-Gel A-5M chromatography of 105,000 g supernatants separated isoleucyl-tRNA synthetase activity into three peaks, with apparent molecular masses (Da) of about 100,000, 350,000 and 10(6) or greater. Similar results were obtained with synthetases specific for glutamic acid, serine and tyrosine. Sucrose-density-gradient centrifugation of yeast supernatants also provided evidence for the existence of synthetase complexes. These data provide the first evidence for the existence of a high-molecular-mass aminoacyl-tRNA synthetase complex in yeast, perhaps similar to those reported in higher eukaryotes.
Explore the source record for details and available documents.