Glutamine cognate codons in rabbit haemoglobin mRNAs

Messenger RNA coding for phenylalanine ammonia-lyase. Characterization and partial purification from cell suspension cultures of Petroselinum hortense

The mRNA coding for phenylalanine ammonia-lyase was partially purified from irradiated cell suspension cultures of parsley (Petroselinum hortense). The product of cell-free translation of the mRNA in a reticulocyte lysate was isolated by immunoprecipitation and compared with the native enzyme subunit. Evidence for the identity, or at least a great similarity, of both was provided by tryptic-peptide and gel-electrophoretic analyses. Under partially denaturing conditions, phenylalanine ammonia-lyase mRNA sedimented as a 20--21-S molecule in a sucrose gradient and had an apparent molecular weight of about 1.05 x 10(6) on a polyacrylamide gel. Approximately two-thirds of the polynucleotide sequence of the mRNA were estimated to be required as coding sequence for the enzyme. We suggest that phenylalanine ammonia-lyase mRNA is unlikely to code for more than of three coordinately induced enzymes.

Aminoacyl-transfer RNA populations in mammalian cells chromatographic profiles and patterns of codon recognition

The chromatographic profiles of 20 aminoacyl-tRNAs from rabbit liver were compared to those of rabbit reticulocytes by reverse phase chromatography and the chromatographic profiles of 20-aminoacyl-tRNAs from bovine liver were compared to those of bovine brain. The two rabbit tissues showed significant differences in the elution profiles of most aminoacyl-tRNAs, while the elution profiles of the aminoacyl-tRNAs from the bovine tissues showed fewer differences. The patterns of codon recognition of several aminoacyl-tRNAs fractionated from rabbit reticulocytes have also been compared to those fractionated from rabbit liver.

The primary structure of rabbit beta-globin mRNA as determined from cloned DNA

The rabbit beta-globin DNA insertion of the hybrid plasmid PbetaG1 (Maniatis et al., 1976) was sequenced by the method of Maxam and Gilbert (1977). A sequence of 576 nucleotides was determined and verified by pyrimidine tract analysis of double-stranded DNA, synthesized in vitro starting from beta-globin mRNA. The derived sequence is in complete agreement with previously reported partial mRNA sequencing data and with the predictions from the primary structure of the protein. Moreover, the globin DNA insertion is missing only 13 nucleotides corresponding to the 5' terminal sequence of the mRNA. The rabbit beta-globin mRNA consists of a coding region of 438 nucleotides, flanked by a 5' noncoding region of 56 nucleotides (including the initiation codon AUG but not the 7-methyl-guanine of the "cap structure") and by a 3' noncoding region of 95 nucleotides (including a UGA termination codon). The features of the mRNA sequence are discussed with specific attention to the selective use of particular codons, the probable existence extensively base-paired segments at the 5' terminal region and the ribosome binding site. The faithful representation of beta-globin mRNA in the PbetaG1 DNA insertion establishes the validity of used cloned DNA, initially derived from double-stranded DNA transcripts of mRNA, for studying the structure of eucaryotic genes.

On the possible modulating role of the isoleucine AUA-codon in bacteriophage MS2 RNA

A set of MS2 mutants were shown to have an additional silent mutation met --> ile at position 108 of the coat protein. As transitions are more frequent than transversions one would have expected an AUA codon in this position in the mutant RNAs. As the AUA codon is one of the best candidates for a modulation role in the control of translation in E. coli, the presence of this AUA in the gene for the protein made in major amounts upon viral infection would impose serious doubt on the theory of modulation. We have directly proven by minifinger-printing of mutant RNA and further analysis of the relevant spots that, in fact, the isoleucine residue at position 108 of the coat protein gene is specified by the non-rate-limiting AUU codon, in agreement with a modulation type of control of protein synthesis.