Cordycepin

Cordycepin is 3′-deoxyadenosine, but is normally used in molecular biology as the triphosphate form. 3′-Deoxyadenosine triphosphate is a chain-terminating nucleotide analogue of ATP that can be incorporated into an RNA by polyadenylate polymerase. This inhibits further elongation of the poly A tail due to the absence of the 3′-hydroxyl group. The cordycepin triphosphate has been used primarily to study the polyadenylation reaction in vitro, where it has allowed this reaction to be resolved into two distinct steps: cleavage of the messenger RNA precursor and the addition of the poly A tail  (1, 2).

References

1.  M. Sheets, P. Stephenson, and M. Wickens (1987) Mol. Cell Biol. 7, 1518–1529. 

2. C. Moore, H. Skolnik-David, and P. Sharp (1986) EMBO J. 5, 1929–1938.