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PubMed1977

The effects of gamma-irradiation on the hydration characteristics of DNA and polynucleotides. III. A comparative NMR study of frozen and liquid solutions.

The effects of gamma-irradiation and changes in the macromolecular structure on the water proton resonance spectra observed in frozen and liwuid solutions have been compared for the DNA and polynucleotide solutions, using H2O or mixed H2O/D2O solvents. The results indicate that in order to obtain information concerning the role of hydration water in mediating the overall radiation damage, the NMR studies must be performed in the frozen state.

Cold Temperature↗
PubMed1975

Poliovirus-induced infectious double-stranded RNA: Effect of RNA-degrading enzymes.

The infectivity of replicative form RNA (RF-RNA) isolated from poliovirus-infected HeLa cells is completely resistant to the action of T-1 RNase but decreases after exposure to RNase A in the presence of 0.3 M NaCl. Under these conditions neither enzyme produces single-stranded nicks in RF-RNA. Three endonuclease-free exonuleases (RNase II, polynucleotide phosphorylase and spleen phosphodiesterase) rapidly destroy the infectivity of single-stranded RNA, but do not alter the infectivity of RF-RNA. It is concluded that RF-RNA does not contain single-stranded ends essential for infectivity. Indirect evidence suggests that all or most of the poly A region at the 3' end of the plus strand of infectious RF-RNA is base-paired to a poly U region at the 5 end of the minus strand.

Base Sequence↗
PubMed1981

[The value of poly-C-specific serum ribonuclease and CEA in the diagnosis of pancreatic carcinoma (author's transl)].

The possible role of poly(C)RNase serum activity and CEA serum level for early detection and differentiation of pancreatic carcinoma and its specificity and valuability were critically analyzed: Serum RNase (median, min-max) with polycytidin as substrate was determined in 13 "normal" patients (14.6 E/ml, 4.3--29.8 E/ml), 16 patients with pancreatic cancer (T3 or metastases) (17.6 E/ml, 6--49-9 E/ml), 15 patients with chronic pancreatitis (9.5 E/ml, 4.9--26.5 E/ml), 7 patients with acute pancreatitis (14.2 E/ml, 5.5--67.3 ng/ml), and 13 patients with other types of malignomas (15 E/ml, 4.3--42.5 E/ml). Serum CEA level was evaluated in 18 "normal" patients (1.15 ng/ml, 0--4.3 ng/ml), 12 patients with pancreatic carcinoma (T3 or metastases) (6.5 mg/ml, 2--456.5 ng/ml), 13 patients with chronic pancreatitis (2.3 ng/ml, 0--8.5 ng/ml), 8 patients with acute pancreatitis (2.7 ng/ml, 0.1--4.6 ng/ml) and 5 patients without operative verification of suspected pancreatic carcinoma (0.9 ng/ml, 0--1.7 ng/ml). The serum RNase activity in pancreatic cancer patients did not show any significant increase in comparison to the other groups, and these patients could not be distinguished from those with the other diseases when excluding other factors influencing serum RNase level such as: Renal insufficiency, nutrition, age, sex. Their CEA level was significantly higher in comparison to the other groups (p less than 0.05). Using 2.5 ng/ml as the limit, the sensitivity was found to be 80% (10/12 of pancreatic carcinomas positive) and the specificity being 70.5% (31/44 of other groups without malignant diseases negative). The presented study and data in the literature show that poly (C) RNase measurement is not useful in early detection of pancreatic carcinoma, but the CEA test could be helpful in the differential diagnosis of pancreatic diseases due to its specificity (70.5%) and seems to be valuable in detection of residual and in monitoring for recurrent pancreatic carcinoma in view of its sensitivity and correlation with the stage of cancer.

Carcinoembryonic Antigen↗
PubMed1979

Self-condensation of activated dinucleotides on polynucleotide templates with alternating sequences.

We have prepared substantial quantities of the alternating polymers poly(U-G) and poly(C-A) and have used them as templates for the self-condensation of ImpApC, ImpCpA, ImpGpU and ImpG. We find that the condensation of ImpGpU and ImpUpG on poly(C-A) is efficient, the condensation of ImpCpA on poly(U-G) is moderately efficient, while the condensation of ImpApC on poly(U-C) proceeds poorly. In many cases, the product is predominantly 3'-5'-linked. These reactions demonstrate unequivocally, for the first time, that template-directed reactions occur in double-helical structures. Furthermore, they describe for the first time a pair of reactions in which each of two complementary polymers facilitates the synthesis of the other. The prebiotic significance of these findings is discussed.

Chemical Phenomena↗
PubMed1981

Condensation of activated diguanylates on a poly(C) template.

We have studied the metal-ion catalysis of a number of reactions of the isomers of ImpGpG on a poly(C) template. In the absence of a catalytic metal ion, oligomers at least up to (pG)20 are obtained from the ImpGpG isomers in a 1-methylimidazole buffer. The Pb2+ ion improves the yield of longer oligomers and changes substantially the distribution of linkage isomers. The Pb2+ ion greatly improves the yield of longer oligomers obtained from G and ImpGpG on a poly(C) template. The self-condensation of ImpGpG in a 2, 6-lutidine buffer is much less efficient than in a 1-methylimidazole buffer. The Zn2+ greatly increases the yield of products from the [3'-5']-linked dimer, but fails to catalyze the formation of long oligomers from the [2'-5']-linked dimer. The bonds formed in the Zn2+-catalyzed self-condensation of ImpG3pG on poly(C) are mainly [3'-5']-linked.

Guanine Nucleotides↗
PubMed1988

The biogeochemical cycle of the adsorbed template. II: Selective adsorption of mononucleotides on adsorbed polynucleotide templates.

Experimental results are presented for the verification of the specific interaction step of the 'adsorbed template' biogeochemical cycle, a simple model for a primitive prebiotic replication system. The experimental system consisted of gypsum as the mineral to which an oligonucleotide template attaches (Poly-C or Poly-U) and 5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP as the interacting biomonomers. When Poly-C or Poly-U were used as adsorbed templates, 5'-GMP and 5'-AMP, respectively were observed to be the most strongly adsorbed species. Moreover, there exists a direct quantitative relationship between the quantity of cytidine or uracil residues in the adsorbed state and the amount of the complementary mononucleotide that is attached to it. NaCl added to the system in order to create conditions of high ionic strength seems to enhance the selectivity of the adsorption of the monmucleotides to these adsorbed templates.

Adsorption↗
PubMed1987

The biogeochemical cycle of the adsorbed template. I: Formation of the template.

Experimental results are presented for the verification of the first adsorption step of the 'adsorbed template' biogeochemical cycle, a simple model for a primitive prebiotic replication system. The adsorption of Poly-C, Poly-U, Poly-A, Poly-G, and 5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP onto gypsum was studied. It was found that under the conditions of the experiment, the polymers have a very high affinity for the mineral surface, while the monomers adsorb much less efficiently.

Adsorption↗
PubMed1979

Effect of synthetic polynucleotides on the growth of transplantable tumours in BALB/c mice.

The effect of BALB/c mice pretreatment with tumour cells (a mammary adenocarcinoma, ADK-1t and an IgA secreting plasmocytoma, MOPC-315) adsorbed with poly I:C, poly I and poly C is examined. Only mice pretreated with cells of both tumours adsorbed with poly I:C and poly C proved to be extensively protected against challenge by homologous untreated tumour cells, whereas this was not so in the case of poly I. A possible explanation of this phenomenon is discussed.

Animals↗
PubMed1986

Template-directed synthesis on short oligoribocytidylates.

The oligonucleotides C(pC)n, n = 4, 5, 6, 7, are efficient templates for the oligomerization of guanosine-5'-phospho-2-methylimidazole (2-MeImpG). They yield oligomeric products that are substantially less regiospecific than those obtained on polycytidylate [poly(C)]. The overall distributions of products obtained on oligo(C)s are generally similar to those of products obtained on oligodeoxycytidylates [oligo(dC)s], but there are substantial differences in the ratios of isomers. The 3'-5'-linked dinucleoside monophosphate GpG efficiently initiates oligomer formation with 2-MeImpG on oligo(C) templates. The pattern of products obtained by chain extension parallels closely that of products obtained directly from 2-MeImpG, except that the former products lack the 5'-terminal phosphate group.

Cytosine Nucleotides↗
PubMedDate not supplied

Template-directed polynucleotide synthesis on mineral surfaces.

Ferric hydroxide, a plausible prebiotic material, strongly adsorbs polynucleotides. We show that adsorption on ferric hydroxide and on several other minerals has no effect, under the conditions studied, on the template-directed oligomerization of guanylic acid on polycytidylic acid.

Biological Evolution↗
PubMed1987

Nucleic acid-like structures. II. Polynucleotide analogues as possible primitive precursors of nucleic acids.

Activated derivatives of purine-containing deoxynucleoside- diphosphates spontaneously oligomerize to produce pyrophosphate- linked oligodeoxynucleotide analogues. These analogues are of potential interest as models of primitive, polynucleotide precursors. The efficiency of oligomerization (ImpdGpIm and ImpdApIm much greater than ImpdIpIm) appears to reflect a combination of stacking forces and the specific geometric orientations of the stacked units. Under favorable conditions, chain lengths greater than 20 have been obtained for oligomers containing pdGp in the absence of a template. In the presence of a complementary template, the activated derivatives of pdGp and pdAp oligomerize much more extensively. An acyclo-analogue of G has also been shown to undergo template-directed oligomerization on pol (C). These observations suggest the possibility that primitive information transfer might have evolved in much simpler systems and that this function was taken over by polynucleotides at a later stage in evolution.

Deoxyribonucleosides↗
PubMed1998

The yeast nuclear gene DSS1, which codes for a putative RNase II, is necessary for the function of the mitochondrial degradosome in processing and turnover of RNA.

The yeast nuclear gene DSS1 codes for a mitochondrial protein containing regions of homology to bacterial RNase II and can act as a multicopy suppressor of a deletion of the SUV3 gene, which encodes an RNA helicase. In order to establish the function of the DSS1 gene in mitochondrial biogenesis we studied RNA metabolism in yeast strains disrupted for SUV3 or DSS1. The results indicate that in the absence of DSS1 the in vitro activity of 3'-5' exoribonuclease is abolished and mitochondrial translation is blocked. In disruption strains harboring intronless mitochondrial genomes steady-state levels of COB mRNA and 16S rRNA were very low, while in the presence of a mitochondrial genome containing the omega intron in the 21S rRNA gene the excised intron accumulates. Moreover we observed an accumulation of precursors of 21S rRNA and the VAR1 mRNA. All these phenotypes are virtually identical to those of strains in which SUV3 is disrupted. We suggest that the DSS1 gene product, like the SUV3 gene product, is a subunit of the yeast mitochondrial degradosome (mtEXO), and that this protein complex participates in intron-independent turnover and processing of mitochondrial transcripts. In addition our studies exclude any role for the NUC1 nuclease in these phenomena.

Animals↗
PubMed2001

Down-regulation of translation driven by hepatitis C virus internal ribosomal entry site by the 3' untranslated region of RNA.

The genome of hepatitis C virus (HCV) is a single-stranded RNA of positive polarity that has a poly(U/C) tract followed by a highly conserved 98-nt sequence, termed the X region, in the 3' untranslated region (UTR). To investigate the effect of the 3'UTR on the HCV translation that depends on the internal ribosomal entry site (IRES), we prepared a deletion HCV RNA, MA delta, that lacked the RNA region from nt 1286 to 8785. A series of MA delta RNAs that differ in the primary structure of their 3'UTR, were generated and examined for their translation efficiencies in reticulocyte lysates. Deletion of the poly(U/C) tract and/or stem-loop structure (SL) 3 region of 3'X resulted in enhancement of the translation efficiency. Translation of MA delta RNA was inhibited by the addition of recombinant polypyrimidine tract-binding protein (PTB). A similar inhibition by PTB, however, was observed when an RNA lacking the poly(U/C) tract or SL3 region was used. The inhibitory effect by PTB was not obvious for MA delta (1041) RNA composed of nt 1 to 1041 but MA delta (8928) RNA composed of nt 1 to 1285 and nt 8786 to 8928. These results suggest that the observed down-regulation of HCV translation by the 3'UTR is mediated by some host factor(s) other than PTB, and that a PTB site for inhibition resides in the coding sequence of nt 1042 to 8928 of MA delta RNA.

3' Untranslated Regions↗
PubMed2005

Chiral selection in oligoadenylate formation in the presence of a metal ion catalyst or poly(U) template.

The lead ion-catalyzed oligomerization of 5'-phosphorimidazolides of D-, L- or racemic DL-adenosine (D-ImpA, L-ImpA and DL-ImpA) gave oligoadenylates up to a pentamer. The oligomers resulting from racemic ImpA were comparable in yields and length to those from chiral D- or L-ImpA. A complex mixture of homochiral and heterochiral oligomers was formed in the reaction from racemic ImpA. Total dimer product from racemic ImpA by the lead ion catalyst showed homochiral selectivity. The reaction catalyzed by uranyl ion yielded oligoadenylates up to 15mer from chiral D- or L-ImpA in over 95% yield. A complex mixture of isomeric oligoadenylates was formed from racemic DL-ImpA in the presence of uranyl ion catalyst in comparable yields to those from D- or L-ImpA. The analysis of the dimer product from DL-ImpA showed that the homochiral 2' -5' linked dimer was selectively formed. D-ImpA polymerized effectively on a poly(U) template, which is exclusively composed of D-uridine, yielding oligoadenylates up to a pentamer. In contrast, L-ImpA or racemic DL-ImpA polymerized far less efficiently on the poly(U) template, demonstrating that chiral selection takes place in the poly(U) template-directed oligoadenylate formation.

Catalysis↗