Selective mRNA degradation by antisense oligonucleotide-2,5A chimeras: Involvement of RNase H and RNase L

Antisense oligonucleotides (ON) allow the specific control of gene expressi on and phosphorothioate derivatives are currently being evaluated for possi ble clinical applications. Numerous second generation ON analogues with imp roved pharmacological properties have been described. Most of them, however , do not recruit RNase H, which is known to increase ON potency by elicitin g the specific degradation of the target RNA. Silverman, Torrence and colle agues have conjugated 2,5A to natural antisense ON and demonstrated the pre ferential cleavage of a target RNA in cell-free and intact cell experiments . We have established for the first time that RNase H-incompetent ON, viz, alpha-anomeric ON analogues, can be converted into sequence-specific nuclea ses upon conjugation to 2,5A. The use of alpha-ON- and beta-ON-2,5A chimera s has allowed us to delineate the part played by RNase H and RNase L in tar get RNA degradation and translation arrest. Finally, the present studies ha ve revealed limitations which are encountered in the choice of a suitable t arget for such ON-2,5A chimeras. (C) Societe francaise de biochimie et biol ogie moleculaire/Elsevier, Paris.