Virus Genes 13:3,229-237, 1996 9 1996 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands. The Putative LEF-1 Proteins From Two Distinct Choristoneura fumiferana Multiple Nucleopolyhedroviruses Share Domain Homology to Eukaryotic Primases JOHN W. BARRETT, 1'2 HILARY A.M. LAUZON, 1 PAOLA SANDRA MERCURI, 1'3 PETER J. KRELL, 2 S.S. SOHI l & BASIL M. ARIF 1 INatural Resources Canada, Canadian Forest Service, Sault Ste. Marie, ON. P6A 5M7 CANADA 2Dept. of Microbiology, University of Guelph, Guelph, ON. N1G 2WI, CANADA SPresent Address: Dipartimento di Sciencze e Technologie Biomediche e di Biometria, Universita' degli Studi dell'Aquila, L'Aquila, ITALY Received June 30, 1996; Accepted August 5, 1996 Abstract. We have identified the lef-1 genes from two multiple nucleopolyhedroviruses that infect natural populations of Choristoneura fumiferana. The lef-I genes in both viruses are directly upstream and in the opposite orientation of their respective ecdysteroid UDP-glucosyltransferase (egt) genes. This gene organization pattern is similar to that found in the genomes of AcMNPV and of OpMNPV. As well, the coding regions and putative protein sequences share a high degree of similarity. Alignment of the predicted amino acid sequences of all known baculovirus lef-1 genes suggests that the LEF-1 proteins have a relatively high degree of conservation, particularly at four identified and distinct do- mains. Moreover, LEF-I proteins bear clear similarity to some eukaryotic primases, predominately at three of the four domains where certain amino acids are absolutely conserved. Key words: CfMNPV, lef-1, CfDEF, eukaryotic primase Introduction Baculoviruses are a group of primarily insect specific viruses. Interest in these viruses stems from the fact that they have been utilized as vec- tors for the expression of foreign proteins and as environmentally benign biological control agents that could potentially replace chemical insecti- cides. Baculoviruses replicate in the nucleus where gene expression is controlled by a regu- lated cascade involving three temporal phases, early, late and very late expression. DNA repli- cation separates the early and the later phases of gene expression. Early genes are required for DNA replication and for the transactivation of later genes. The late expression factor-1 (lef-l) The nucleotide sequence data reported in this paper have been submitted to the Genbank nucleotide database and have been assigned the accession numbers U23421 and U23422. gene of Autographa californica multiple nucleo- polyhedro virus (AcMNPV) is expressed early in infection and was shown to be essential for late and very late gene expression (1). The open reading frame (ORF) was located immediately upstream and transcribed in the opposite orienta- tion of AcMNPV egt. Although the precise role of lef-1 in late gene expression remains to be de- termined, omission of the DNA fragment con- taining lef-1 from an AcMNPV library curtailed most late and very late gene expression, but not early gene expression. However, these observa- tions were derived from analysis of CAT expres- sion of reporter constructs under the control of early, late and very late promoters (1). Other in- vestigators found that this CAT assay did not distinguish between genes whose products were directly involved in DNA replication and conse- quently necessary for late gene expression and