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Biomedical subjects

Y Groner

Publications and source records attributed to Y Groner.

At least 109 records · Page 6Linked to original sources
PubMed1976

Methylated, blocked 5' termini of yeast mRNA.

mRNAs of the yeast, Saccharomyces cerevisiae, have modified 5' termini similar but not identical with those present in the higher eukaryotes. Poly(A)-containing RNA isolated from spheroplasts or from polysomes of cells labeled with [methyl-3H]methoionine or 32Pi contain methylated, blocked 5'-terminal structures of composition: m7G(5')pppAp and m7G(5')pppGp, occurring in a relative distribution of 75% and 25%, respectively. Furthermore there is no N6-methyladenosine nor any other methylated nucleoside in the entire molecule of poly(A)-containing RNA. Experiments with a mutant, temperature-sensitive for the transport of mRNA to cytoplasm, suggest that the methylation and addition of the blocking group take place in the nucleus and that the genetic lesion in the mutant does not affect these mechanisms.

Methionine↗
PubMed1976

5'-Capping structures of Artemia salina mRNA and the translational inhibition by cap analogs.

The mRNA of the brain shrimp Artemia salina has two types of blocked methylated 5'-terminal structures (caps). About 75% of the mRNA molecules have the 5'-end structure of m7G5'ppp5'-AmpGp and about 25% have the structure of m7G5'ppp5'GmpGp. The only other type of methylated residue found in Artemia mRNA is N6-methyladenosine and which is located at internal positions along the mRNA chain. Translation of Artemia cyst or nauplius poly(A)-rich mRNA in wheat-germ extracts was found to be inhibited by 7-methylguanosine 5'-monophosphate, a chemical analog of the cap, as well as by snythetic caps such as m7G5'ppp5'Gm. On the other hand, the elongation activity on endonegous mRNA in an Artemia cell-free system was not sensitive to 7-methylguanosine 5'-monophosphate.

Aminoacylation↗
PubMed1975

Chromatin as a template for RNA synthesis in vitro.

RNA transcribed in vitro from myeloblast chromatin by exogenously added RNA polymerase B predominantly consists of short chains that remain in hybrid structure with the template; the remainder of the product is free RNA of heterogeneous size. Addition of polyanions during synthesis caused an increase in the size and amount of free RNA with a concomitant decrease in the proportion of small RNA. The large molecular weight RNA is derived from the short RNA chains, which are synthesized de novo during the reaction in vitro. The effect of polyanions on the size and nature of the product may be related to structural changes induced in the template rather than to an inhibition of nuclease activity.

Animals↗
PubMed1975

Synthesis of RNA containing a methylated blocked 5' terminus by HeLa nuclear homogenates.

RNA synthesized in vitro by HeLa nuclei contains a variety of blocked methylated 5'-terminal structures that can be grouped into four general types: (a) m(7)GppN(m)p...; (b) m(7)GppN(m)pM(m)p...; (c) m(7)GpppN(m)p...; and (d) m(7)GpppN(m)pM(m).... Both N(m) and M(m) can be either one of the four 2'-O-methylated nucleosides. The relative amounts of the N(m) species are G = 45%, A = 25%, U = 20%, and C = 10%.

Cell Nucleus↗
PubMed1975

AMV RNA transcription in cell-free systems and properties of in vitro chromatin-directed RNA synthesis.

In this report we have presented evidence that viral sequences in the genome of AMV-infected myeloblasts can be transcribed in vitro. The RNA products synthesized in either nuclei isolated from these cells or by eukaryotic RNA polymerase B from the isolated chromatin contained approximately 1% virus-specific sequences. This result, which is in agreement with the fraction of viral RNA in infected cells (Garapin et al. 1971), is higher than expected from a random transcription of the genome, and thus shows that a degree of selectivity in transcription is maintained in both systems. The inhibition of synthesis of viral sequences in nuclei by alpha-amanitin as well as the finding that RNA polymerase B catalyzed the synthesis of viral sequences from chromatin support the hypothesis that the expression of viral information is mediated by nucleoplasmic RNA polymerase. An investigation of the properties of the chromatin-directed products led to the suggestion that RNA synthesis in vitro was initiated on single-stranded or denatured regions of the template; a limiting factor in the synthesis of large molecular weight RNA from isolated chromatin appeared to be the extent of the denatured region available to the enzyme. These findings are consistent with the suggestion that gene activation in eukaryotic organisms results from the unwinding of segments of chromatin DNA (Crick 1971).

Amanitins↗
PubMed1974

The in vitro synthesis of avian myeloblastosis viral RNA sequences.

Isolated nuclei, prepared from myeloblasts of chicks infected with avian myeloblastosis virus, synthesize RNA sequences present in avian myeloblastosis viral RNA. These sequences are also formed during transcription of chromatin, isolated from myeloblasts, by DNA-dependent RNA polymerases purified from Escherichia coli or calfthymus. In the latter case, transcription is alpha-amanitin sensitive. Formation of hybrids between RNA and avian myeloblastosis virus DNA probes has been monitored by the combined use of ribonucleases A, T(1), and H, and ribonucleases specific for single strands.

Animals↗