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PubMed1976

Polynucleotide displacement reactions: detection by interferon induction.

A large variety of displacement reactions between homopolynucleotides and complexes thereof has been demonstrated by interferon induction data obtained in primary rabbit kidney cell cultures superinduced with metabolic inhibitors. The polymers involved in these helix-coil displacement studies were: poly(adenylic acid), poly(inosinic acid), poly(cytidylic acid), poly(uridylic acid), poly(ribothymidylic acid), polylaurusin, poly(7-deazaadenylic acid), poly(7-deazainosinic acid), poly(5-bromocytidylic acid), and poly(5-bromouridylic acid). As monitored by ultraviolet absorbance-temperature profiles, all displacement reactions were directed toward the formation of the helix with the higher thermal stability. Concomitantly, the resulting helix was invariably more active as interferon inducer than the reactant helix, except for some reactions in which poly(7-deazaadenylic acid) was involved. For the latter reactions both the reactant and resultant helices were inactive as interferon inducer. The interferon induction data revealed that all displacement reactions proceeded to completion within 1 h even at temperatures well below the Tm of the reactant helix. The helix-coil displacement reaction could also be monitored by sucrose velocity gradient analysis, and, as evidenced for poly(A)-2poly(I) + 2poly(C) leads to 2poly(I)-poly(C) + poly(A), readily occurred at the cellular level, presumably at the cell surface.

Animals↗
PubMed1976

Triple-helical polynucleotides. Mixed triplexes of the poly(uridylic acid)-poly(adenylic acid)-poly(uridylic acid) class.

By the techniques of interferon induction in primary rabbit kidney cells "superinduced" with metabolic inhibitors, ultraviolet absorbance-temperature profiles, sensitivity to pancreatic ribonuclease A, and sucrose velocity gradient ultracentrifugation, a number of reactions between double-helical RNA and single-stranded RNA or DNA homopolymers were investigated. The polymers involved in these studies were poly(adenylic acid), poly(uridylic acid), poly(ribothymidylic acid), poly(5-bromouridylic acid), poly(deoxythymidylic acid), poly(deoxyuridylic acid), poly(3-methyluridylic acid), poly(2'-O-methyluridylic acid), and poly(2'-azido-2'-deoxyuridylic acid). Two different reaction courses, both leading to the formation of triple helices, were noted: (1) poly(Ux)-poly(A) + poly(Uy) leads to poly(Ux)-poly(A)-poly(Uy) if the Tm of poly(Ux)-poly(A) was higher than the Tm of poly(Uy)-poly(A); (2) poly(Ux)-poly(A) + poly(Uy) leads to poly(Uy)-poly(A)-poly(Ux) if the Tm of poly(Ux)-poly(A) was lower than the Tm of poly(Uy)-poly(A). In these equations, the homopolymer written to the left of poly(A) implies Watson-Crick hydrogen bonding whereas the polymer to the right of poly(A) is involved in Hoogsteen hydrogen bonding.

Animals↗
PubMed1975

Association of the polyadenylate segment of messenger RNA with other polynucleotide sequences in mouse sarcoma 180 polyribosomes.

Limited digestion of polysomal RNA with pancreatic ribonuclease releases a structure consisting of poly(A) associated with other polyribonucleotide sequences. This complex can be purified by oligo(dT)-cellulose chromatography. Heating for formamide treatment causes the dissociation of fragments free of poly(A) from the poly(A)-containing components. The two types of fragments tend to reassociate under annealing conditions, and this association is prevented by poly(U). Control experiments indicate that this structure is not an artifact generated during the manipulations. The same structure can be obtained by limited RNase digestion of polyribosomes, followed by deproteinization. The results suggest that the mRNA in polyribosomes may have a defined configuration caused by the interaction of the poly(A) sequence with another segment of the RNA.

Adenine↗
PubMed1975

Polynucleotide analogs: acrylic acid and maleic acid copolymers of 1-vinyluracil and 9-vinyladenine.

Radical-induced copolymerization of 1-vinyluracil and maleic anhydride gave, after hydrolysis, a polymer containing a 1:1 monomer ratio of 1-vinyluracil-maleic acid. Gamma-Ray-induced copolymerization of 1-vinyluracil with acrylic acid gave a polymer with a ratio of 1:1.7. Similar treatment of 9-vinlyadenine and acrylic acid resulted in a polymer with a 1:3.2 ratio. These three compounds are potent stimulants of poly (uridylic acid) coded polyphenylalanine synthesis in an in vitro cell free system purified from Escherichia coli MRE 600. The double-stranded polymer, poly(inosinic acid)-poly(cytidylic acid), also stimulates polyphenylalanine synthesis in this assay.

Adenine↗