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R C Moore

Publications and source records attributed to R C Moore.

At least 55 records · Page 3Linked to original sources
PubMed1988

Thyrotropin alters the utilization of thyroglobulin's hormonogenic sites.

We injected rabbits and guinea pigs with bovine thyrotropin (TSH) daily for 3 days, while controls received saline. All animals received sodium [125I]iodide on the second day, and thyroglobulin was purified from the thyroids of each group by gel filtration. Hormonogenic tryptic peptides from each S-cyanoethylated thyroglobulin preparation were isolated by high performance liquid chromatography, and their amino acid sequences were determined, permitting their localization within the thyroglobulin polypeptide chain by comparison with cDNA-derived sequences from bovine and human thyroglobulins. Thyroglobulins from the saline-injected rabbits and guinea pigs contained the same four major hormonogenic sites, designated A-D, previously described (Dunn, J. T., Anderson, P. C., Fox, J. W., Fassler, C. A., Dunn, A. D., Hite, L. A., and Moore, R. C. (1987) J. Biol. Chem. 262, 16948-16952). In both species, sites A and C were the major loci for thyroxine and triiodothyronine, respectively. However, site D in the guinea pig had a greater ratio of [125I]thyroxine to [127I]thyroxine than did site A, whereas the reverse was true in the rabbit. TSH administration produced the following changes in thyroglobulins of both species, relative to controls: 1) an increase in the ratio of [125I]triiodothyronine to [125I] thyroxine (rabbit, 0.29 versus 0.17; guinea pig, 0.19 versus 0.08), with the increase in triiodothyronine principally at site C; 2) a marked increase in 125I/127I and in thyroxine formation at site D (14.1% of thyroglobulin's thyroxine versus 9.8% in rabbits, 24 versus 13% in guinea pigs); 3) a corresponding decrease in thyroxine formation at site A (33 versus 43% in rabbits, 30 versus 46% in guinea pigs); and 4) a sharp increase in conversion of thyroglobulin's N-terminal 125I-labeled approximately 20 kDa hormone-rich iodopeptide, which contains site A, to a 125I-labeled approximately 15-kDa (rabbit) or 125I-labeled approximately 13-kDa (guinea pig) form, reflecting probable peptide bond cleavage. Our results show that TSH alters both the structure of the thyroglobulin molecule and the priority of utilization of its hormonogenic sites. We conclude that these changes are important to TSH's enhancement of thyroid hormone synthesis.

Amino Acid Sequence↗
PubMed1988

An investigation using inhibition of G2 repair of the molecular basis of lesions which result in chromosomal aberrations.

Cultures of JU56 cells were irradiated with 2.5 Gy X-rays and 16 h later the cultures were exposed to a moderately inhibitory dose of 1-beta-D-arabinofuranosylcytosine (ara-C) or aphidicolin (APC) and to colcemid, for 2 h. The c-metaphases collected for examination had therefore been exposed to X-rays in G1 or early S, and to the repair inhibitors APC and ara-C during the latter half of G2. It was found that treatment of cells irradiated early in cell cycle, that is, in G1 and early S, with APC or ara-C in G2, (1) reduced the frequency of chromatid and chromosome exchanges below that of cells treated with X-rays alone, (2) produced no more chromatid breaks and gaps than were seen in unirradiated cells, (3) increased the number of chromosome fragments and gaps in a more than additive fashion, and (4) produced only an additive effect, by comparison with the effect of X-rays and drug given separately, on the total number of chromosomal aberrations.

Animals↗
PubMed1988

Synergism of 1-beta-D-arabinofuranosylcytosine with itself and aphidicolin.

JU56 cells have been exposed to 1-beta-D-arabinofuranosylcytosine (ara-C) in S phase, and again to aphidicolin (APC) or ara-C during G2, and examined for chromosomal aberrations at c-metaphase. It was found that the two exposures acted synergistically in the production of chromosomal lesions of both the chromatid and isochromatid type. The results were interpreted as indicating that inhibition of the G2 repair system prevented the repair of DNA single-strand regions produced by the incorporation of ara-C during semi-conservative DNA synthesis.

Aphidicolin↗
PubMed1987

The sites of thyroid hormone formation in rabbit thyroglobulin.

Rabbit thyroglobulin (Tg) was labeled in vivo with 125I and purified by gel filtration. Separation by high performance liquid chromatography (HPLC) of tryptic digests of S-cyanoethylated Tg yielded four major iodothyronine-containing peaks, designated A, B, C, and D. These were further purified on HPLC and sequenced for identification of amino acid residues and for location of the iodothyronine by 125I counting. The published primary structure for bovine Tg, derived from cDNA sequencing of the Tg gene (Mercken, L., Simons, M.J., Swillens, S., Massaer, M., and Vassart, G. (1985) Nature 316, 647-651), permitted tentative location of the rabbit hormonogenic peptides within the Tg polypeptide chain. Site A, corresponding to bovine residue 5, contained 44% of Tgs [125I]T4 (thyroxine) and 25% of its [125I]T3 (triiodothyronine); its specific activity of iodine was higher than that for other sites, indicating priority of iodination. Site B, containing 24% of Tgs [125I]T4 and 18% of its [125I]T3, corresponded to bovine residue 2555. Site C, at the third residue from the C terminus (bovine residue 2748), was the major T3 site, accounting for over 50% of Tgs [125I]T3. The amino acid sequence around this site shows less homology among different animal species than do those flanking the other hormonogenic sites. Site D accounted for 17% of Tgs [125I]T4 and corresponded to bovine Tyr-1291, in the midportion of Tgs polypeptide chain. The three major T4-forming sites had the sequence Asp-Tyr (sites B and D) or Glu-Tyr (site A), while the sequence Ser-Tyr-Ser appeared to favor T3 synthesis (site C), suggesting an important influence of primary structure on hormonogenesis. We conclude that site A is the major T4-forming site and site C the major T3-forming one, but others are available and offer the opportunity for flexibility in meeting different demands for hormone formation.

Amino Acid Sequence↗
PubMed1987

Different effects of 1-beta-D-arabinofuranosylcytosine and aphidicolin in S-phase cells--chromosome aberrations, cell-cycle delay and cytotoxicity.

Some effects of a 2-h exposure to either aphidicolin (APC) or cytosine arabinoside (ara-C) on S-phase cells of the cell line JU56 have been measured. At a concentration of 1.5 X 10(-5) M of either drug, incorporation of tritiated thymidine into log-phase cultured was reduced by 97-99%. A 2-h exposure to either drug at the same concentration induced chromosome aberrations in cells in S when they subsequently reached mitosis. However, exposure to ara-C induced small numbers of aberrations per damaged cells, and most cells were undamaged. Exposure to APC induced gross chromosomal damage (pulverized chromosomes) in damaged cells. More cells were delayed, and for longer, after exposure to APC than after exposure to ara-C. The results of clonal assays were consistent with the assumption that chromosome aberrations are the proximal cause of reproductive cell death. In the case of ara-C, the results of this and a previous study are consistent with the assumption that cell death and chromosome aberrations are correlated with incorporation of ara-C into DNA in S-phase cells, but that these biological effects manifest themselves only with doses when inhibition of semi-conservative DNA synthesis is greater than 97%.

Animals↗
PubMed1987

MYC oncogene involved in a t(8;22) chromosome translocation is not altered in its putative regulatory regions.

We have cloned the translocation-associated MYC gene from the Burkitt lymphoma cell line (BL2) with a t(8;22) chromosomal translocation and have determined the nucleotide sequence of the first exon and of the 3' and 5' flanking regions, where sequences with putative regulatory functions have been identified. The nucleotide sequence of the 5' flanking region, which contains regions of DNase hypersensitivity and binding sites for putative regulatory proteins, is the same as that of the normal MYC. Accordingly, mutations in these regulatory regions are not required for the transcriptional deregulation of MYC in the BL2 cell line. The nucleotide sequence of the first exon is similar to that of the normal MYC [Gazin, C., Dupont de Direchin, S., Hampe, A., Masson, J. M., Martin, P., Stehelin, D. & Galibert, F. (1984) EMBO J. 3, 383-387] and has the coding capacity for a 188-residue polypeptide. However, six nucleotide changes that occur in the middle of this reading frame could result in amino acid substitutions. We also have cloned and sequenced the t(8;22) chromosomal breakpoint that is located 10 kilobases 3' of the MYC exon 3 and near the C lambda 3 gene on chromosome 22. Sequences with homology to immunoglobulin joining signals occur close to the breakpoint both on chromosome 8 and 22, providing further evidence that the immunoglobulin joining enzymes may be involved in the recombinations associated with a variety of chromosomal translocations in B and T cells.

Amino Acid Sequence↗
PubMed1987

The synergistic effect of aphidicolin on the yield of X-ray-induced chromosome aberrations throughout the cell cycle in JU56 cells.

The effect of a 2-h post-treatment with aphidicolin at a dose sufficient to inhibit DNA synthesis on the yield of X-ray-induced chromosomal aberrations throughout the cell cycle was measured. Exposure to aphidicolin during and after irradiation brought about an increase in exchanges in cells irradiated in G2, in sister unions only in cells irradiated in S, and in all chromosome aberration types (fragments, sister unions, and dicentrics) in cells irradiated in G1. It is suggested that, during G1 and G2 but not during S inhibiting the repair enzyme alpha-polymerase brings about the conversion of some X-ray-induced DNA lesions to double-strand which can then take part in aberrations.

Animals↗
PubMed1986

A common mechanism of chromosomal translocation in T- and B-cell neoplasia.

The chromosomal breakpoint involved in the t(8;14)(q24;q11) chromosome translocation in the SKW-3 cell line, which directly involves the 3' flanking region of the c-myc gene, was cloned and sequenced. The breakpoint on chromosome 8 mapped to a position 3 kb 3' of c-myc while the chromosome 14 breakpoint occurred 36 kb 5' of the gene for the constant region of the alpha chain of the T-cell receptor (TCR). The translocation resulted in a precise rearrangement of sequences on chromosome 8 and what appears to be a functional J alpha segment on chromosome 14. Signal sequences for V-J joining occurred at the breakpoint positions on both chromosomes 14 and 8, suggesting that the translocation occurs during TCR gene rearrangement and that it is catalyzed by the enzymatic systems involved in V-J joining reactions. The involvement of c-myc in the translocation and the association of joining signals at the breakpoints provides a parallel to the situation observed in the translocations involving c-myc and the immunoglobulin loci in B-cell neoplasms and suggests that common mechanisms of translocation and oncogene deregulation are involved in B- and T-cell malignancies.

B-Lymphocytes↗
PubMed1986

Dose relationships between different effects of aphidicolin in JU56 cells.

Some effects of aphidicolin have been investigated in relationship to dose, in a permanent cell line, JU56. Inhibition of semi-conservative DNA synthesis occurred at concentrations greater than 3 X 10(-7) M. In this respect the cells were about as sensitive as L1210 and HeLa cells, and more than 10-fold more sensitive than PHA-stimulated human peripheral blood leucocytes. Delay of progress of cells through G2 occurred at concentrations which inhibited synthesis to about 2% of control levels. Chromatid aberrations appeared in cells at concentrations which decreased synthesis to 5%. Synergism with X-rays in the production of chromatid aberrations occurred at doses which reduced semi-conservative synthesis to 40% of control levels. Isochromatid aberrations appeared in cells continuously exposed to aphidicolin in G2 at concentrations which reduced synthesis to 5% of control units.

Animals↗
PubMed1985

Chromosome aberration types in cells irradiated in G1 with nutrient depletion.

When cultured JU56 cells were blocked in G1 by nutrient depletion, irradiated and then subcultured, a subpopulation of cells at the next metaphase contained not only chromosome-type aberrations, but also triradials and chromatid exchanges. The triradials were found to be the result of chromosome-type breaks in three chromosomes, followed by exchange of chromatids. Obviously, chromatid exchanges and dicentrics could arise by the same mechanism. Triradials and chromatid exchanges were not found in cells irradiated in G1 without nutrient depletion. It appears, therefore, that nutrient depletion can affect the capacity of cells to repair X-ray induced damage. The types of aberrations suggest that the lesions which form them cause real physical discontinuities of the chromosomes, with movement of the broken ends before exchange formation.

Animals↗
PubMed1984

Chromosome aberration types in Chinese hamster (CHO) cells X-irradiated in S and G1.

The different types of chromosome aberrations found after a single dose of 2.5 Gy of hard X-rays were scored in Chinese hamster (CHO) cells irradiated in early G1, late G1, early S and late S phase. Chromatid-type aberrations were found throughout S, and chromosome-type aberrations were found in early S. Sister unions were found in early S and G1, and were more common in early than in late G1. Sister unions manifested themselves as an increase in the number of apparent acrocentric chromosomes, with an accompanying apparent increase in chromosome number. It is suggested that previous studies have failed to observe sister unions in this cell type because of the difficulty of distinguishing between sister unions and acrocentric chromosomes.

Animals↗
PubMed1983

The role of iodination in the formation of hormone-rich peptides from thyroglobulin.

Reduced thyroglobulins from several animal species contain hormone-rich iodopeptides of 20,000-26,000 and 15,000-18,000 daltons. The present study has investigated the role of iodination in their production. Experimental approaches have included: iodination in vitro of thyroglobulin from rabbit thyroid slices incubated with [3H]leucine and subsequent analysis of 3H distribution by gel electrophoresis; iodination in vitro of low iodine thyroglobulin from a human goiter, followed by isolation of the major iodopeptides and quantitation of their peptide content; and injection of iodine-deficient rats with Na125I and assessment of the distribution of isotope among the iodopeptides at successive time intervals. From these experiments the following general pattern has emerged: 1) at low levels of iodine (less than 5 atoms/molecule of thyroglobulin) in vitro or at short time intervals after iodine administration in vivo (less than 4 h), the principal iodinated component of reduced thyroglobulin is a approximately 230,000-dalton peptide; 2) with moderate increases in iodine (5-40 atoms/molecule) or longer time intervals after administration (greater than or equal to 4 h) there is less of the 230,000-dalton iodopeptide, and an iodothyronine-rich approximately 20,000- to 26,000-dalton iodopeptide appears; 3) at higher levels of iodine (greater than 40 atoms/molecule) the amount of approximately 230,000-dalton iodopeptide decreases further, the amount of 20,000- to 26,000-dalton iodopeptides may decrease, and an iodothyronine-rich 15,000- to 18,000-dalton peptide appears. Progressive iodination gives the same changes in distribution of peptide material among these iodopeptides as it does in iodine distribution, and the changes seen with iodination in vitro are similar to those occurring over time in vivo. We conclude that during the process of iodination discrete peptide bonds of thyroglobulin are cleaved to produce the hormone-rich iodopeptides. This is probably a normal part of thyroglobulin maturation in vivo and may be a necessary event preceding hormone formation.

Animals↗