Identification, transcription and sequence analysis of the Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) DNA polymerase gene

Sequence analysis of a 6.4 kb DNA region from the Spodoptera littoralis mul tinucleocapsid nucleopolyhedrovirus (SpliNPV) revealed a large open reading frame (ORF) encoding a predicted polypeptide of 998 amino acid (aa) residu es with a molecular mass of 114.93 kDa, located between 47.2-52.3 m.u. on t he SpliNPV genome. Comparative sequence analyses demonstrated that the ORF encodes a DNA polymerase gene (dnapol) that contains conserved exonuclease domains and DNA polymerase motifs found in many prokaryotic, eukaryotic, an d viral replicative DNA polymerases. A second ORF, ORF138, located between the lef-3 and dnapol, encodes a 138 aa polypetide that is homologous to ORF 66 of the Autographa californica MNPV (AcMNPV). SpliNPV DNA polymerase shar es an overall aa sequence identity of 39% with that of AcMNPV. A 3.0 kb Spl iNPV dnapol-specific transcript was detected initially at 2 hpi and became abundant 48 hpi by Not-them blot analysis. The transcription initiation sit e was mapped to an NPV early promoter element, ACGT. 3' RACE demonstrated t hat the SpliNPV dnapol transcript terminated at the polyadenylation signal AATAAA. Sequence analysis suggested that-the SpliNPV-dnapol-and-the-dnapol- of the NPV of S. litura (SpltNPV) are closely related.