Showing papers on "Intron published in 1969"
TL;DR: In this article, the number of 4, 18 and 26 s RNA cistrons present in purified nuclear and mitochondrial DNA of Saccharomyces cerevisiae has been determined and the significance of these findings to the continuous synthesis of ribosomal RNA during the cell cycle of yeast is discussed.
218 citations
211 citations
TL;DR: Quantitative studies indicate that each of the methylated sequences is probably present twice in a molecule of the 23S RNA, so that these sequences encompass about 5% of the nucleotides present in the entire molecule.
Abstract: The primary structures of the 16S and 23S ribosomal RNAs of Escherichia coli have been studied. Nucleotide sequences have been determined which occur in specific areas close to the small numbers of methylated nucleotides which are present in these molecules. Fragments containing these methylated nucleotides were obtained by digestion of radioactive RNA substrates with T1 ribonuclease. Such digestion products were fractionated by high-voltage electrophoresis in two dimensions.
The 23S RNA yielded predominantly 11 methylated oligonucleotides on digestion, and the 16S RNA gave rise to 6 methylated components. Nucleotide sequence analysis of these products was carried out, and the nature of the modified nucleotides occurring in each product was also examined. It was found that some of the sequences contained several modified components positioned close to each other. Quantitative studies indicate that each of the methylated sequences is probably present twice in a molecule of the 23S RNA, so that these sequences encompass about 5% of the nucleotides present in the entire molecule. It is postulated that extensive repetition of nucleotide sequences occurs within the 23S RNA.
136 citations
TL;DR: Human and mouse 28 s ribosomal RNA when extracted at room temperature have identical mobility in polyacrylamide gel electrophoresis, but when heated, the mobility of the human type changes, whereas that of the mouse does not.
98 citations
TL;DR: Renaturation kinetics showed that the sequence length molecular weight of Neurospora mitochondrial DNA is more than 66 × 106, therefore, the genes for 25 s and 19 s RNA are repeated at least four times in the mitochondrial DNA.
74 citations
TL;DR: The data suggest strongly that light coordinately stimulates splicing of all four psbA introns, and it is demonstrated that this response to light is mediated by photosynthetic electron transport.
Abstract: Efficient splicing in vivo of most self-splicing group I introns is believed to require proteins, raising the possibility that splicing could be regulated; however, examples of such regulation have been lacking. The Chlamydomonas reinhardtii chloroplast psbA gene contains four large group I introns that self-splice efficiently in vitro, but only under nonphysiological conditions. The psbA gene encodes the D1 protein of photosystem II, which is synthesized at very high rates in the light in order to replace photodamaged protein. We show that psbA pre-mRNAs, containing one or more introns, accumulate in wild-type cells in the dark, apparently due to rate-limited splicing. Analysis of the pre-RNAs indicates that splicing of the four introns does not follow a strict order. Exposure of cells to light induced rapid (15-20 min) decreases in precursor levels of approximately 3-5-fold (depending on the intron), which were accompanied by transient increases in free intron levels. Because light also stimulated psbA transcription approximately 2-fold over the same period, the data suggests that light increases the splicing efficiency of psbA introns approximately 6-10-fold. Similar estimates of the extent of light stimulation were obtained by analyzing precursor decay rates in the presence of actinomycin D. The effect of light is specific for psbA introns, because levels of unspliced 23S pre-RNA did not decrease. The light-induced increase in psbA pre-RNA processing was abolished by inhibitors of photosynthetic electron transport, but not by the ATP synthesis inhibitor, carbonylcyanide m-chlorophenylhydrazone, which actually promoted pre-RNA processing in the dark. Finally, nonphotosynthetic mutants, including the tscA-lacking photosystem I mutant, H13, did not show evidence of light-stimulated RNA processing. However, the light response was restored in photosynthetic transformants of H13 that had been complemented with the tscA gene. These data suggest strongly that light coordinately stimulates splicing of all four psbA introns. Moreover, they demonstrate that this response to light is mediated by photosynthetic electron transport. The implications of these results for the regulation of psbA gene expression are discussed.
72 citations
65 citations
TL;DR: Many diverse RNA's are synthesized in the lampbrush stage oöcyte of Xenopus, as shown by the presence of different nucleotide sequences in the RNA population.
Abstract: Many diverse RNA's are synthesized in the lampbrush stage oocyte of Xenopus, as shown by the presence of different nucleotide sequences in the RNA population. This fact has been established by hybridizing lampbrush stage oocyte RNA with an isolated nonrepetitive fraction of Xenopus DNA.
61 citations
53 citations
TL;DR: Late after infection, pulse-labeled nuclear and cytoplasmic virus-specific RNA possess the same base composition and the same nucleotide sequences.
TL;DR: The pulse-chase experiments show that the methylated part of 40 S RNA is converted to 28 S and 18 S RNA, the 18 SRNA appearing as such very early, and the 28 S RNA appearing after some intermediate processing steps involving 30–32 S species.
TL;DR: Experiments are presented which firmly establish the ribosomal precursor nature of the 38-S RNA molecule found in the yeast Schizosaccharomyces pombe by showing the kinetics of methylation are similar to those of uracil labeling.
TL;DR: It is proved that in a cell-free system from Escherichia coli, bacteriophage f2 RNA initiates the synthesis of three proteins and that two of these are the phage coat protein and RNA polymerase.
TL;DR: The structure of ribosomal RNA has differentiated appreciably in the course of evolution and the over-all structure as opposed to the nucleotide sequence tends to be conserved during evolution.
TL;DR: An E. coli ribosome system which forms only the first peptide bond of f2 proteins is described, showing directly that ribosomes can independently attach to two sites on the f2 RNA.
TL;DR: The correspondence between RNA codons and amino acids, determined with aminoacyl-tRNA from embryos and adults, does not differ grossly for the twelve amino acids examined, however, both Xenopus embryo and adults differ from E. coli aminoacyL-t RNA in relative response to certain synonym trinucleotides.
TL;DR: H(3)-labeled purified 16S and 23S ribosomal RNA's and transfer RNA's were found to hybridize exclusively with the H strand of the separated complementary strands of B. subtilis DNA, indicating that these RNA's are transcribed in vivo from a strand with a composition similar to that from which messengerRNA's are copied and presumably by the same mechanism.
Abstract: H3-labeled purified 16S and 23S ribosomal RNA's and transfer RNA's were found to hybridize exclusively with the H strand of the separated complementary strands of B. subtilis DNA. These results indicate that these RNA's are transcribed in vivo from a strand with a composition similar to that from which messenger RNA's are copied and presumably by the same mechanism.
TL;DR: It has been concluded that the major base sequences of ribosomal RNA's in reticulocytes and liver are the same.
TL;DR: Several steps in the synthesis in vitro of infectious bacteriophage RNA can now be described, and the interaction of these components and the mechanims of the reaction appears to be considerably more complex than was proposed in earlier models.
Abstract: Several steps in the synthesis in vitro of infectious bacteriophage RNA can now be described. The reaction catalyzed by the Qβ RNA polymerase is known to involve several components, including the enzyme, host cell factors, Qβ RNA template, and the strand complementary to the Qβ RNA. The interaction of these components and the mechanims of the reaction appears to be considerably more complex than was proposed in earlier models.