RIFT-VALLEY FEVER VIRUS L-SEGMENT - CORRECTION OF THE SEQUENCE AND POSSIBLE FUNCTIONAL-ROLE OF NEWLY IDENTIFIED REGIONS CONSERVED IN RNA-DEPENDENT POLYMERASES

The sequence of Rift Valley fever virus L segment that we published in a previous paper was erroneous in the 3'-terminal region of the antig enomic RNA molecule. Here, we have shown that the L segment is in fact 6404 nucleotides long and encodes a polypeptide of 237.7K in the vira l complementary sense. Sequence comparisons performed between the RNA- dependent RNA polymerases of 22 negative-stranded RNA viruses revealed the existence of two novel regions located at the amino termini of th e proteins and conserved only in the polymerases of bunya- and arenavi ruses. In the region conserved in all RNA-dependent polymerases, corre sponding to the so-called 'polymerase module', we identified a new mot if, designated premotif A, common to all RNA-dependent polymerases, as well as amino acids located in the region between motifs preA and A w hich are strictly conserved for segmented negative-stranded RNA viruse s. Using the recently released coordinates of human immunodeficiency v irus reverse transcriptase and the alignment between all RNA-dependent polymerases in the 'polymerase module', we have determined the positi on of the conserved residues in these polymerases and discuss their po ssible functions in light of the available structural information.