Identification of a novel functional nuclear localization signal in the protein encoded by open reading frame 47 of Bombyx mori nucleopolyhedrovirus.

BM47 is encoded by open reading frame 47 of Bombyx mori nucleopolyhedrovirus (BmNPV). BM47 was localized in the nucleus of BmNPV-infected cells. In the present study, we investigated a novel nuclear localization signal (NLS) for BM47 transport and accumulation in the nucleus. By expressing various regions of BM47 fused to enhanced green fluorescent protein (EGFP), we demonstrated that residues 117-148 are necessary for mediating nuclear localization of BM47. Site-directed mutation analysis showed that the two basic residue clusters at positions 117-120 (¹¹⁷RKRR) and 144-148 (¹⁴⁴RKR-K) constitute an authentic NLS for BM47 localization. Finally, we observed that two clusters of basic residues were conserved in BM47 homologues of group-I nucleopolyhedroviruses.