Nucleic Acids Research, 1995, Vol. 23, No. 24 5000-5005
© 1995
Articles |
Stereodifferentiation—the effect of P chirality of oligo (nucleoside phosphorothioates) on the activity of bacterial RNase H
Polish Academy of Sciences, Centre of Molecular and Macromolecular Studies, Department of Bioorganic Chemistry Sienkiewicza 112, 90-363 Loòdz, Poland
*To whom correspondence should be addressed
Received September 28, 1995. Accepted November 13, 1995.
P stereoregular phosphorothloate analogs of pentadecamer 5'-dfAGATGTTTGAGCTCO-3' were synthesized by the oxathiaphospholane method. Their diastereomeric purity was assigned by means of enzymatic degradation with nuclease P1 and, independently, with snake venom phosphodiesterase. DNARNA hybrids formed by phosphorothioate oligonucleotides (PS-oligos) with the corresponding complementary pentadecaribonucleotide were treated with bacterial RNase H. The DNA-RNA complex containing the PS-oligo of [all-RP] configuration was found to be more susceptible to RNase H-dependent degradation of the pentadecaribonucleotide compared with hybrids containing either the [all-Sp] counterpart or the so called ‘random mixture of diastereomers’ of the pentadeca(nucleoside phosphorothioate). This stereodependence of RNase H action was also observed for a polyribonucleotide (475 nt) hybridized with these phosphorothioate oligonucleotides. The results of melting studies of PS-oligo-RNA hybrids allowed a rationalization of the observed stereodifferentiation in terms of the higher stability of heterodimers formed between ollgorlbonucleotides and [all-RP]-oligo(nucleoside phosphorothioates), compared with the less stable heterodimers formed with [[all-Sp]-oligo{nucleoside phosphorothioates) or the random mixture of diastereomers.