Nucleotide sequence in tRNA Val-2a from baker's yeast

Dosage suppressors of a benomyl-dependent tubulin mutant: evidence for a link between microtubule stability and cellular metabolism

To identify factors important for the regulation of microtubule stability in yeast, dosage suppressors of the hyperstable microtubule phenotype of the budding yeast tub2-150 beta-tubulin mutation were isolated. Of the two suppressors reported here, one (JSN2) encodes a tRNAVal, and the other (JSN3) is an antimorphic allele of the methionine biosynthesis transcription factor Met4p. Furthermore, growth of tub2-150 mutants and suppression of tub2-150 mutants by JSN3 are sensitive to levels of methionine in the growth medium. We explore several possible explanations for these findings, including the potential involvement of the general amino acid control and the involvement of Cbflp, a component of yeast kinetochores that is also necessary for Met4p-mediated transcription.

Thiolated nucleotides in yeast transfer RNA

By culturing Saccharomyces cerevisiae in growth medium containing Mg35SO4, we have determined the extent and variation of tRNA thiolation in this yeast. We find that 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U)1 is the major, if not only, thiolated derivative in S. cerevisiae tRNA. In addition, a comparison of the chromatographic mobility of mcm5s2Up on cellulose thin layers with those reported for unknown uridine derivatives found in purified yeast tRNA digests, leads to the conclusion that at least two of these tRNAs contain this modification.

Modified bases in tRNA: the structures of 5-carbamoylmethyl- and 5-carboxymethyl uridine

The crystal structures of two nucleosides, 5-carbamoylmethyluridine (1) and 5-carboxymethyluridine (2), were determined from three-dimensional x-ray diffraction data, and refined to R = 0.036 and R = 0.047, respectively. Compound 1 is in the C3'-endo conformation with chi +5.2 degrees (anti), psiinfinity = +63.4 degrees and psialpha = +180.0 degrees (tt); 2 is in the C2'endo conformation with chi +49.4 degrees (anti), psiinfinity -60.5 degrees and psialpha +60.0 degrees (gg). For each derivative, the plane of the side chain substituent is skewed with respect to the plane of the nucleobase; for 1, the carboxamide group is on the same side of the uracil plane vis a vis the ribose ring; for 2, the carboxyl group is on the opposite side of this plane. No base pairing is observed for either structure. Incorporation of structure 1 into a 3'-stacked tRNA anticodon appears to place 08 within hydrogen bonding distance of the 02' hydroxyl of ribose 33, which may limit the ability of such a molecule of tRNA to "wobble".

Cloning of yeast transfer RNA genes in Escherichia coli

Four thousand Escherichia coli clones containing yeast DNA inserted into the plasmid pBR313 have been isolated. Of these, 175 clones were identified as carrying yeast transfer RNA genes. The initial analysis of the inserted transfer RNA genes via the colony hybridization technique with individual radioactive transfer RNA species is reported. The data indicate that yeast transfer RNA genes are not highly clustered, although some clustering exists. In addition, it was observed that the reiteration number of different transfer RNA genes may vary extensively.

Nucleotide sequence (n=159) of the amino-acid-accepting 3'-OH extremity of turnip-yellow-mosaic-virus RNA and the last portion of its coat-protein cistron

The experiments described in this paper and the following one establish the sequence of the 3'-OH terminal 159 nucleotides of turnip yellow mosaic virus RNA. Uniformly 32P-labeled turnip yellow mosaic virus RNA was partially digested with T1 ribonuclease and the fragments were fractionated by polyacrylamide gel electrophoresis. Fragments originating from the 3'-OH end of the RNA molecule were identified by testing for the 3'-terminal oligonucleotide, C-COH, after total U2 ribonuclease hydrolysis. Once identified, the 3'-OH terminal fragments were sequenced by the methods of Sanger et al. The first 51 nucleotides of the longest of the sequenced fragments (158 nucleotides) extends into the 3'-terminal part of the coat protein cistron. The coat protein cistron is followed by a stretch of 108 untranslated nucleotides whose function, though still unknown, is probably linked to the tRNA-like properties which have been attributed to the 3'-OH extremity of this viral RNA. Two possible secondary structures are proposed for the sequence and the implications of the findings with regard to the tRNA-like properties of the extremity are discussed.