[Formation of specific T3-RNA-polymerase complexes with oligoribonucleotides and inhibition of DNA-dependent RNA synthesis].

It was shown previously that E. coli RNA polymerase and T7 RNA polymerase being incubated with oligonucleotides of different length derived from RNA endonuclease hydrolysate bind selectively to certain oligonucleotides with the length larger than or equal to 5. The data presented demonstrate that T3 RNA polymerase also binds selectively from the isoplith mixtures certain oligonucleotides starting from pentanucleotides. Adding of excess of T3 RNA polymerase it was possible to exhaustively extract the recognizable oligonucleotides from the isoplith mixture. However, the exhausted by T3 RNA polymerase mixture of pentanucleotides still contained those which are bound selectively by T7 and E. coli RNA polymerases. The data suggest that various RNA-polymerases recognize different oligoribonucleotides. It was shown that T3 DNA inhibits the selective binding of penta-or heptaribonucleotides to T3 RNA polymerase competing obviously for the enzyme. The T3 RNA polymerase bound penta- or heptanucleotides inhibit DNA-dependent RNA synthesis carried out by the enzyme; the isoplith mixtures which do not contain T3 RNA polymerase bound oligonucleotides are deprived of the inhibitory properties. Only those isoplith mixtures contain T3 RNA polymerase bound oligonucleotides which were derived from symmetrically transcribed RNA which have obviously promoter simulating sequences. The data provide evidence that T2 RNA polymerase binds selectively the oligonucleotides mimicking the promotor recognition sites.