Structural and Ionic Requirements for Self-cleavage of Virusoid RNAs and trans Self-cleavage of Viroid RNA
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Excerpt
Certain circular and low-molecular-weight, single-stranded plant pathogenic RNAs can self-cleave at specific sites in vitro in the presence of Mg++ (Buzayan et al. 1986a; Hutchins et al. 1986; Prody et al. 1986; Forster and Symons 1987a). This property is considered to be important in their replication in vivo by a rolling-circle mechanism. All of these self-cleavage reactions generate 5′-OH and 2′,3′-cyclic phosphodiester termini in what is essentially a transphosphorylation reaction involving attack by the free 2′-OH group on the 3′,5′-phosphodiester linkage (Fig. 1A). These self-cleavage reactions are clearly different from the self-splicing reactions involved in the removal of introns from rRNA and mRNA precursors that produce excised fragments with 5′-phosphate and 3′-OH termini (Cech and Bass 1986; Sharp 1987).
Self-cleavage occurs in the plus and minus RNAs derived from the 247-nucleotide avocado sunblotch viroid (ASBV) (Hutchins et al. 1986), the 359-nucleotide linear satellite RNA of tobacco ringspot virus (sTRSV) (Buzayan...
