Molecular characterization of human group C rotavirus genes 6, 7 and 9

Genes 6, 7 and 9 of human group C rotavirus 'Bristol' strain, encoding non- structural proteins (NSP) 3, 1 and 2, respectively, were cloned and sequenc ed. Human group C rotavirus genome segment 6 is 1350 bp and contains a sing le ORF of 1231 nucleotides (encoding 402 amino acids), Genome segment 7 is 1270 bp and encodes a protein of 394 amino acids and genome segment 9 is 10 37 bp and encodes a 312 amino acid protein. The human group C rotavirus gen es 6, 7 and 9 showed 78, 67 and 88% sequence identity, respectively, to the corresponding porcine group 6 rotavirus genes, The derived protein sequenc es were compared with those of the porcine 'Cowden' group C and mammalian g roup A rotavirus strains. The human group C rotavirus NSP1 protein sequence is one amino acid longer than the porcine group C equivalent. In common wi th group A and porcine group C rotaviruses, the human group C rotavirus NSP 1 protein has a zinc finger motif, Human group 6 rotavirus NSP2 has two hyd rophobic heptad repeat regions, a basic, RNA-binding domain and a basic, pr oline-rich region. Human group C rotavirus NSP3 has both single- and double -stranded RNA-binding domains and several hydrophobic heptad repeat regions , one of which forms a leucine zipper. This work completes the molecular ch aracterization of the non-structural proteins of a human group C rotavirus, Phylogenetic analysis of all the nonstructural genes of group A, B and C r otaviruses suggests that these viruses have diverged at a constant rate fro m a common ancestor.