Selective Strand Annealing and Selective Strand Exchange Promoted by the N-terminal Domain of Hepatitis Delta Antigen

Zhi-Shun Huang,Wen-Huey Su,Jui-Ling Wang,Huey-Nan Wu

doi:10.1074/jbc.m207938200

Zhi-Shun Huang, Wen-Huey Su + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m207938200

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Abstract

We have previously shown that the N-terminal domain of hepatitis delta virus (NdAg) has an RNA chaperone activity in vitro (Huang, Z. S., and Wu, H. N. (1998) J. Biol. Chem. 273, 26455-26461). Here we investigate further the basis of the stimulatory effect of NdAg on RNA structural rearrangement: mainly the formation and breakage of base pairs. Duplex dissociation, strand annealing, and exchange of complementary RNA oligonucleotides; the hybridization of yeast U4 and U6 small nuclear RNAs and of hammerhead ribozymes and cognate substrates; and the cis-cleavage reaction of hepatitis delta ribozymes were used to determine directly the role of NdAg in RNA-mediated processes. The results showed that NdAg could accelerate the annealing of complementary sequences in a selective fashion and promote strand exchange for the formation of a more extended duplex. These activities would prohibit NdAg from modifying the structure of a stable RNA, but allow NdAg to facilitate a trans-acting hammerhead ribozyme to find a more extensively matched target in cognate substrate. These and other results suggest that hepatitis delta antigen may have a biological role as an RNA chaperone, modulating the folding of viral RNA for replication and transcription.

Highlights

RNA chaperones are defined as proteins that aid in the folding of RNA by preventing misfolding or by resolving misfolded structures [11]
Strategy—Previously we had shown that the N-terminal domain of hepatitis delta antigen (NdAg) modulates the cis-cleaving activity of Hepatitis delta virus (HDV) genomic RNA fragments and activates the trans-cleavage reaction between hammerhead ribozymes and cognate substrates in vitro [16]
To further investigate the basis of RNA chaperone activity, purified NdAg was assayed for the ability to promote the annealing of complementary sequences in RNA oligos and complicated RNA molecules in dilute solutions, and to accelerate strand exchange between an RNA duplex and a competing sequence

Summary

Introduction

RNA chaperones are defined as proteins that aid in the folding of RNA by preventing misfolding or by resolving misfolded structures [11]. Hepatitis delta antigen can modulate the cis-cleaving activities of HDV genomic RNA fragments and facilitate a trans-acting hammerhead ribozyme to find its target in RNAs of various sequences and lengths [16].

Results

Conclusion