Viral RNA from fall armyworm (Spodoptera frugiperda) cells infected with Autographa californica nuclear polyhedrosis virus contains cap structures. Most of the cap labeled in vivo with [3H]methionine or 32pI cochromatographed on DEAE-cellulose with the -5 charge marker; a minor com onent appeared at -4 net charge. The former is probably a cap 1 structure (m GpppXmYp), and the latter is probably a cap 0 (m7GpppXp). On the basis of relative labeling of the two caps with [3H]adenosine and [H]guanosine, we concluded that each cap contained at least one adenosine residue in addition to guanosine and, therefore, that cap 0 contained m7GpppAp. Cleavage of [3H]methionine-labeled viral RNA with tobacco acid pyrophosphatase released a labeled component that cochromatographed on polyethyleneimine-cellulose with m7Gp, confirming the m7GpppX linkage in the cap. These results were also seen with host polyadenylated RNA. The caps appeared in nearly equal abundance in viral polyadenylated and nonpolyadenylated RNAs. The ratio of 32p; incorporated into the cap to that incorporated into mononucleotides suggested average lengths for the polyadenylated and non-polyadenylated RNAs of 1,800 and 1,200 nucleotides, respectively.

The nucleotide sequence of a 1587 bp region lying within the HindIII-Q fragment of Autographa californica multiple nucleocapsid nuclear polyhedrosis virus (AcMNPV) DNA has been determined. It begins in the EcoRI-S-EcoRI-X region, continues to the HindlII-P/Q boundary and contains an open reading frame that codes for a polypeptide of 240 amino acids (p26). This open reading frame is also included in the 1100 and 1500 base transcripts previously mapped to this region. The sequence reveals that the 5' ends of the 1100 and 1500 base transcripts are located 20 bp downstream from the end of a putative TATA box (TAATTAAAT) and 19bp upstream from thetranslation start codon (ATG) of the p26 open reading frame. The translation termination codon (TAA) falls in the immediate 5' flanking region of the major late p 10 gene of AcMNPV, 3bp downstream from the putative TATA box. The probable polyadenylation site for the 1100 base transcript lies 23bp downstream from the cap site for the 750 and 2500 base transcripts encoding the pl0 protein. The 5' flanking region of the p26 open reading frame contains the EcoRI site-rich region, hr5, whose sequence is included here. The EcoRI site-rich region, hrs, consists of six imperfect tandem repeats of a sequence that includes the EcoRI recognition site. These direct repeats also include many inverted repeats.