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At least 685 records · Page 38Linked to original sources
PubMed1995

Growth regulation by all-trans-retinoic acid and retinoic acid receptor messenger ribonucleic acids expression in gastric cancer cells.

Retinoic acid has been recognised as a pivotal compound in cell differentiation, proliferation and malignant transformation. We investigated the effects of all-trans-retinoic acid on cell growth and the expression of retinoid nuclear receptor mRNAs in gastric cancer cells in vitro. Cell growth was quantified by measuring total cellular DNA. The growth of two of the five gastric cancer cell lines tested (SC-M1 and TSGH9201) was inhibited by all-trans-retinoic acid at concentrations ranging from 1 x 10(-8) M to 1 x 10(-6) M. Growth inhibition was associated with G0/G1 phase arrest as determined by flow cytometric analysis. Northern blot analysis showed that all five cell lines expressed mRNA for retinoic acid receptors alpha and retinoic x receptor alpha and beta. Retinoic acid receptor beta mRNA was only expressed in TSGH9201 and TMK-1 gastric cancer cell lines. Two RAR gamma mRNA transcripts (3.2 and 3.0 kb) were detected in SC-M1 and TSGH9201 cells. RA-resistant cells had markedly decreased levels of the 3.2 kb RAR gamma transcript. All-trans-retinoic acid had a cytostatic effect on the growth of some gastric cancer cells, which may be associated with the expression of retinoic acid receptors.

Cell Cycle↗
PubMed1985

Sequence content of oligo(uridylic acid)-containing messenger ribonucleic acid from HeLa cells.

Oligo(uridylic acid)-containing [oligo(U+)] RNA was isolated from poly(adenylic acid)-containing [poly(A+)] mRNA from HeLa cells by using either formaldehyde pretreatment or poly(A) removal, both of which resulted in increased accessibility of oligo(U)-rich sequences to a poly(A)-agarose affinity column. In this report, we compared the sequence content of oligo(U+) RNA with that of molecules lacking oligo(U) [oligo(U-) RNA] by their relative hybridization to cDNA reverse-transcribed from poly(A+) mRNA and by comparison of their in vitro translation products synthesized in a rabbit reticulocyte lysate. Formaldehyde-modified poly(A+) RNA, treated to remove the formol adjuncts, was inactive as a template for in vitro protein synthesis; consequently, only depolyadenylated RNA, which retains its translatability, could be used in the translation studies. The hybridization kinetic experiments revealed that oligo(U+) RNA contained most of the sequence information present in oligo(U-) RNA but at a reduced level (ca. 25%), the majority of the oligo(U+) RNA sequences being poorly represented in the cDNA. This result was supported by one- and two-dimensional gel analysis of their in vitro translation products which showed that oligo(U+) RNA, although less effective as a template for translation than oligo(U-) RNA, coded for proteins, the most abundant of which were encoded by rare messages not highly represented in oligo(U-) RNA or the total poly(A+) RNA. Although some minor products were synthesized by both oligo(U+) and oligo(U-) RNA, at least 33 proteins were unique to or highly enriched in the pattern of products directed by oligo(U+) RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Specificity of the photoreaction of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen with ribonucleic acid. Identification of reactive sites in Escherichia coli phenylalanine-accepting transfer ribonucleic acid.

In order to test the potential of psoralen photoaddition for the probing of RNA conformation at sequence resolution, we have analyzed the specificity of the reaction of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) with Escherichia coli tRNAPhe. The sites of HMT covalent addition have been identified by a combination of analytical techniques involving chemical cleavage of the tRNAPhe molecule at the m7G site and gel electrophoresis of RNase T1 digests together with paper electrophoretic characterization of HMT-modified nucleotides and oligonucleotides. In addition, we have taken advantage of the alteration of the cleavage rate of pancreatic RNase adjacent to a photoadduct. HMT photoaddition shows a very high preference for uracil residues. However, important differences in HMT photoreactivity are observed for various U sites of the tRNAPhe molecule. Reactivity of specific bases has been correlated with partial melting of the molecule. Data available so far indicate a strong preference of the photoreactive probe for a "loose" helical conformation as compared with a tight helix, whereas a random coil appears poorly reactive.

Binding Sites↗
PubMed1977

Characterization of purified poly(adenylic acid)-containing messenger ribonucleic acid from Saccharomyces cerevisiae.

Yeast poly(adenylic acid)-containing messenger RNA was isolated from total cellular RNA by affinity chromatography on poly(uridylic acid)-cellulose. The relative complexity of the isolated yeast mRNA was assessed by hybridization analysis with complementary DNA synthesized from the isolated messenger RNA (mRNA) with viral reverse transcriptase. Approximately 25% of the mRNA hybridized at an apparent Crt1/2 of 5 X 10(-3) mol sl.(-1), while the remainder hybridized at an average Crt1/2 of 10(-1) mol sl.-1. Poly(adenylic acid)-containing yeast mRNA was translated in vitro in a wheat germ cell-free extract, and the major polypeptides synthesized have the same molecular weight as the major proteins present in the cell. Four of these proteins were identified by coelectrophoresis and immune precipitation to be pyruvate kinase, enolase, aldolase, and glyceraldehyde-3-phosphate dehydrogenase. These data demonstrate in agreement with the hybridization results that yeast contains major mRNA species and that some of the glycolytic enzyme mRNAs make up part of the major fraction. A procedure is outlined for the preparation of yeast mRNA which is essentially free of ribosomal RNA contamination and is further enriched in the major mRNAs present in the cell.

Centrifugation, Density Gradient↗