Host Cell Proteins Bind Specifically to the Capsid-Cleaved 5' End of Leishmaniavirus RNA(1)

Saiz, Margarita; Ro, Young-Tae; Wirth, Dyann F.; Patterson, Jean L.

Leishmaniavirus (LRV) is a double-stranded RNA (dsRNA) virus that persistently infects some strains of the protozoan parasite, Leishmania. LRV generates a short transcript, corresponding to the 5' end of the positive- sense RNA (320 nt), via a cleavage event mediated by the viral capsid protein on the full-length positive sense RNA transcript. To address the possibility that the RNA cleavage represents a regulatory mechanism for maintaining persistent infection, the interactions between Leishmania cytoplasmic proteins and in vitro synthesized viral transcripts were studied. In gel mobility shift experiments, three specific RNA/protein complexes were formed between cellular proteins and the cleaved viral transcript, and three major proteins were labeled by UV cross-linking. No protein binding activity was observed for either the short (320 nt) or full-length RNA transcripts. However, the two cleavage reaction products were able to form stable RNA/RNA complexes. We present a model in which the virus is targeting its own transcript for cleavage to promote binding of host factors to cryptic domains inaccessible in the full-length transcript.