Stereodifferentiation--the effect of P chirality of oligo(nucleoside phosphorothioates) on the activity of bacterial RNase H

Nucleic Acids Res. 1995 Dec 25;23(24):5000-5. doi: 10.1093/nar/23.24.5000.


P stereoregular phosphorothioate analogs of pentadecamer 5'-d(AGATGTTTGAGCTCT)-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. DNA-RNA 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 oligoribonucleotides 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / metabolism
  • Base Sequence
  • Enzyme Activation
  • Molecular Sequence Data
  • Oligonucleotides / chemical synthesis
  • Oligonucleotides / chemistry*
  • Oligonucleotides / metabolism
  • Ribonuclease H / metabolism*
  • Stereoisomerism


  • Oligonucleotides
  • Ribonuclease H