MAPPING THE TACARIBE VIRUS Z PROTEIN BINDING SITES ON THE L POLYMERASE PROTEIN

M.T. FRANZE-FERNÁNDEZ , M. WILDA , N. LÓPEZ , J.C. CASABONA

Salamanca, Spain

Conferencia; XIII International Conference on Negative Strand Viruses; 2006

The arenavirus Tacaribe ( TacV )  comprises a single phylogenetic lineage together with the four South  American pathogenic producers of severe hemorrhagic disease.  TacV genome encodes four proteins : the  precursor of the viral  glycoproteins, the nucleocapsid protein, the large L protein ( 2210 aminoacids ) containing sequence motifs of RNA-dependent RNA polymerases of negative-strand RNA viruses and a 95-aminoacid RING-finger protein called Z. Using a reverse-genetic system we have previously demonstrated that TacV-Z protein inhibits viral RNA synthesis by direct interaction with the L polymerase ( J.Virol. 77:10383-10393 :  2003 ). To delineate the regions involved in the interaction with Z, C-terminal, N-terminal and site-directed mutations in L were characterized for their ability to form a complex with Z as detected by coimmunoprecipitation. It was found that Z-L interactions were not disrupted by deletions of up to 550 aminoacids within the C-terminal sequence of the L molecule whereas a further 220 aminoacids truncation comprising approximately 50 aminoacids of the C-terminal portion of  L-predicted region III, reduced the interaction to about 7 % of WT L. Site-directed mutagenesis within region III identified nine aminoacids important for binding Z. Complex formation studies using L mutants with N-terminal deletions suggested a second region of interaction within aminoacids 1-392.