Poly(A) Tail Recognition by a Viral RNA Element Through Assembly of a Triple Helix

Abstract

Self-Protection Mechanism Kaposi's sarcoma–associated herpesvirus (KSHV) causes an AIDS-associated cancer. During its lytic phase, the virus produces a noncoding polyadenylated nuclear RNA that accumulates to high levels in infected cells. This occurs because a helix-loop-helix element, called ENE within the RNA, that contains a uridine-rich internal loop, sequesters the poly(A) tail, preventing the initiation of RNA decay. Mitton-Fry et al. (p. 1244 ) have determined the 2.5 angstrom structure of the ENE core bound to the RNA. Instead of just binding to the uridine-rich loop, as was expected, the poly(A) tail interacts with the loop and lower stem to form a triple helix to prevent decay. Similar mechanisms may protect other noncoding RNAs from rapid turnover.