Expression and sequence analysis of gene 7 of the IDIR agent (group B rotavirus): Similarity with NS53 of group A rotavirus

Abstract

The seventh genomic segment of the IDIR strain of group B rotavirus was cloned, sequenced, and expressed in vitro in order to evaluate the gene coding assignment by comparison with group A rotaviruses (GAR). Viral genomic RNA for these reactions was obtained directly from fecal specimens of infected infant rats. IDIR virus gene 7 (IDIRg7) contained 1276 bp. Both 5' and 3' termini resembled those reported for other IDIR virus genomic segments. Two open reading frames (ORF) were predicted from the gene sequence: a long ORF from bases 258-1217 and a short ORF from bases 41-385. The first AUG of the long ORF was flanked by sequences associated with highly efficient translation, but less efficient translation was predicted for the short ORF. In vitro transcription and translation of IDIRg7 demonstrated a product consistent with polypeptide synthesis from the long ORF but not the short ORF. Convalescent rat antibody directed against the IDIR agent specifically immunoprecipitated the IDIRg7 protein and indicated that the in vitro translation product was indeed encoded by the virus genome. Thus, the untranslated 5' region of IDIRg7 was longer than that previously described for any major rotavirus product. Comparison of the IDIRg7 sequence indicated 51% similarity and 18% identity with the amino acid residues of NS53 of the SA11 strain of GAR. However, the sequence of IDIRg7 did not share the putative zinc binding region postulated for NS53 of rotavirus groups A and C. It will be of interest in future experiments to evaluate the function of the IDIRg7 product following large-scale synthesis by alternative expression systems such as vaccinia or baculovirus. © 1994 Academic Press, Inc.