The rates of the major steps in the molecular mechanism of RNase H1-dependent antisense oligonucleotide induced degradation of RNA

Antisense oligonucleotides (ASOs) are most commonly designed to reduce targeted RNA via RNase H1-dependent degradation, however kinetic parameters for ASO-mediated targeting and subsequent cleavage and degradation of RNA in living cells are poorly understood. In this manuscript we use an inducible minigene system to determine the time course of ASO activity in the cell. Estimates of the time required for the ASO to enter and traverse the cell, scan the target mRNA, bind the cognate site, recruit RNase H1 and initiate cleavage, are presented in the context of transcription and mRNA processing rates. Data are also presented which indicate that rates for RNase H1-dependent ASO-mediated degradation of the targeted RNAs are different for nuclear-retained versus RNAs exported to the cytoplasm and that the level of RNase H1 in the cell and cellular compartments is limiting to the rate of ASO activity. In both cellular compartments RNase H1 ASOs essentially double the endogenous rates of clearance of the target RNA. Overexpression of Escherichia coli RNase H1 or the presence of multiple cognate sites each further increase the rate of target RNA degradation.