CLONING AND NUCLEOTIDE SEQUENCING OF THE S4 GENOME SEGMENT OF AVIAN REOVIRUS S1133

The sequence of RNA genome segment S4 of the avian reovirus (ARV) stra in S1133 was determined. S4 RNA is 1185 base pairs long and contains o ne open reading frame encoding a protein of 367 amino acid residues (4 0.6kDa), the similar size as the known S4 gene product (sigma NS), wit h a net charge of -1 at neutral pH. The S4 RNA sequence possesses a pe ntanucleotide sequence UCAUC at the 3'-terminus of its plus strand lik e in ARV S1 and S3 segments and ten segments of mammalian reovirus (MR V). The predicted amino acid sequence comparison revealed that the hom ology is 44.02%, 45.71%, and 42.33% for ARV sigma NS and three serotyp es of MRV sigma NS, respectively. The relatively high content of alpha -helix structure in the C-terminal portion of ARV sigma NS suggests th at this protein may functionally relate to MRV sigma NS. Northern blot hybridization showed that a P-32-labeled cDNA insert S4-49 from ARV S 4 RNA cross-hybridized with the corresponding RNA segments of all seve n strains of ARV tested.