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At least 595 records · Page 33Linked to original sources
PubMed1972

Hybridization of Rous sarcoma virus deoxyribonucleic acid polymerase product and ribonucleic acids from chicken and rat cells infected with Rous sarcoma virus.

Rous sarcoma virus (RSV)-specific ribonucleic acid (RNA) in virus-producing chicken cells and non-virus-producing rat cells infected with RSV was studied by hybridization with the endogenous deoxyribonucleic acid (DNA) product of the RSV virion DNA polymerase system. By hybridizing the total DNA product with excess virion RNA, the product DNA was separated into hybridized ("minus") and nonhybridized ("plus") DNA. The "minus" DNA was complementary to at least 20% of the RNA from RSV which remained of high molecular weight after denaturation. A maximum of approximately 65% hybridization was observed between "minus" DNA and RSV RNA or RSV-infected chicken cell RNA. A maximum of about 60% hybridization was observed between "minus" DNA and RSV-infected rat cell RNA. RSV-infected chicken cells contained RSV-specific RNA equivalent to about 6,000 virions per cell. RSV-infected rat cells contained RSV-specific RNA equivalent to approximately 400 virions per cell. Neither cell type contained detectable RNA complementary to virion RNA. The RSV-specific RNA in RSV-infected rat cells did not appear to be qualitatively different from that in RSV-infected chicken cells.

Animals↗
PubMed1972

Distribution of deoxyribonucleic acid complementary to the ribonucleic acid of avian myeloblastosis virus in tissues of normal and tumor-bearing chickens.

(3)H-labeled 70S ribonucleic acid (RNA) from purified avian myeloblastosis virus (AMV) was used as a probe in deoxyribonucleic acid (DNA)-RNA hybridization experiments to detect the presence of DNA complementary to the AMV genome in various tissues from noninfected normal chickens and from chickens infected with AMV. There was a remarkable constancy in the average cellular concentration of virus-specific DNA found in every tissue from the same uninfected chicken, and even in different chickens from the same strain. In contrast, different tissues from chickens bearing AMV-induced kidney tumors (embryonal nephromas) revealed an unequal distribution in the average virus-specific DNA content per cell. The increase was limited to tumor cells and to tissues that contain target cells for AMV, i.e., red blood cells, kidney cells, and possibly leukocytes. The red blood cells from AMV-infected chickens suffering from acute myeloblastic leukemia, although producing no virus, contained as many viral genome equivalents per cell as did leukemic myeloblasts known to produce large quantities of AMV. An increased viral DNA content was observed in the target cells of chickens that did not show any sign of tumor formation 6 months after infection with AMV. This study demonstrates that vertically transmitted viral DNA is uniformly and stably distributed among all tissues of the offspring, but that horizontal infection after hatching results in an increase in viral DNA content only in some dividing, target tissues that may or may not give rise to neoplasias.

Animals↗
PubMed1976

Poly(uridylic acid) sequences in messenger ribonucleic acid of HeLa cells.

The poly(uridylic acid [poly(U)] sequences of 30 to 40 nucleotides found in the heterogeneous nuclear ribonucleic acid (RNA) Of HeLa cells are also present in the poly(adenylic acid) [poly(A)] containing messenger RNA (mRNA) of these cells. Twenty-five percent of the total poly(U) sequences in the cell are found in the cytoplasm after HeLa cells have been labeled for 2.5 h with 32P. This value is close to 40% if only poly(A) containing RNA molecules of the cell are considered. The distribution of poly(U) sequences parallels that of poly(A) sequences in different size classes of cytoplasmic messenger RNA. From the concentrations and lengths of the two sequences it can be estimated that about 20% of the poly(A) containing mRNA molecules could contain one poly(U) sequence. Several lines of evidence have been developed to rule out poly(U) containing heterogeneous nuclear RNA (HnRNA) as the source of the poly(U) sequences in cytoplasm. Poly(U) sequences are also found in RNA molecules of the nucleus and cytoplasm which do not contain poly(A). Although poly(U) sequences are most abundant in nuclear RNA species lacking poly(A), they are well represented in a class of RNA molecules in cytoplasm which lack poly(A), but which otherwise resemble the polysomal mRNA of HeLa cells.

Base Sequence↗
PubMed1979

Cyanobacterial ribonucleic acid polymerases recognize lambda promoters.

We compared the initiation specificities in vitro of deoxyribonucleic acid-dependent ribonucleic acid polymerases purified from two cyanobacteria, Fremyella diplosiphon and Anacystis nidulans, and from Escherichia coli. A restriction fragment made from lambda deoxyribonucleic acid was used as a template. The cyanobacterial and E. coli ribonucleic acid polymerases recognized the same lambda promoters but exhibited different sensitivities to the inhibitor heparin, suggsesting differences in the structure of the initiation complexes.

Bacteriophage lambda↗
PubMed1983

Determination of base pairing in ribonucleic acid by Fourier-transform infrared spectrometry: yeast ribosomal 5S ribonucleic acid.

Fourier-transform infrared (FT-IR) spectra of yeast ribosomal 5S RNA have been acquired at several temperatures between 30 and 90 degrees C. The difference spectrum between 90 (bases unstacked) and 30 degrees C (bases stacked) provides a measure of base stacking in the RNA. Calibration difference spectra corresponding to stacking of G-C or A-U pairs are obtained from "reference" FT-IR spectra of poly(rG) X poly(rC) minus 5'-GMP and 5'-CMP or poly(rA) X poly(rU) minus 5'-AMP and 5'-UMP. The best fit linear combination of the calibration G-C and A-U difference spectra to the 5S RNA (90-30 degrees C) difference spectrum leads to a total of 25 +/- 3 base pairs (17 G-C pairs + 8 A-U pairs) for the native yeast 5S RNA in the absence of Mg2+. In the presence of Mg2+, an additional six base pairs are detected by FT-IR (one G-C and five A-U). FT-IR melting curve midpoints show that A-U and G-C pairs melt together (65 and 63 degrees C) in the presence of Mg2+ but A-U pairs melt before G-C pairs (47 vs. 54 degrees C) in the absence of Mg2+.

Base Composition↗
PubMed1980

A novel enzymatic activity of phenylalanyl transfer ribonucleic acid synthetase from baker's yeast: zinc ion induced transfer ribonucleic acid independent hydrolysis of adenosine triphosphate.

Phenylalanyl-tRNA synthetase from baker's yeast in the presence of phenylalanine or other amino acids misactivated by the enzyme, ATP, and low concentrations of Zn2+ is able to hydrolyze ATP to AMP and PPi very efficiently. After dialysis of the enzyme against ethylenediaminetetraacetic acid (EDTA), this amino acid dependent but tRNAPhe-independent hydrolysis is suppressed to negligible levels. The ATP hydrolysis can be restored by the addition of Zn2+ to the EDTA-dialyzed enzyme. During aminoacylation of tRNAPhe the Zn2+-induced ATP hydrolysis parallels the aminoacylation reaction, leading to nonstoichiometric production of AMP. Mechanistically, we conclude that Zn2+ can be bound to phenylalanyl-tRNA synthetase and can influence the stability of ATP if an activatable amino acid is present. The influence of Zn2+, if any, on the aminoacylation of tRNAPhe is not known. In practice, this side reaction is of the utmost importance in all cases in which the fate of ATP during aminoacylation is followed, especially if the stoichiometry of ATP consumption in relation to Phe-tRNAPhe formation has to be determined.

Adenosine Triphosphate↗