title: Inter-subunit interactions of the Autographa californica M nucleopolyhedrovirus RNA polymerase.
abstract: Autographa californica M nucleopolyhedrovirus transcribes genes using two DNA-directed RNA polymerases; early genes are transcribed by the host RNA polymerase II, and late and very late genes are transcribed by a viral-encoded multisubunit RNA polymerase. The viral RNA polymerase is composed of four proteins: Late Expression Factor-4 (LEF-4), LEF-8, LEF-9, and P47. The predicted amino acid sequences of lef-9 and lef-8 contain motifs that are similar to those that participate at the catalytic center of known RNA polymerases. The requirement for the motif present in LEF-8 in late gene expression has been previously demonstrated. We have assessed the requirement of specific residues within the motif in LEF-9 for late gene expression. The conserved aspartic acid residues within the LEF-9 motif, corresponding to those essential for activity of the Escherichia coli RNA polymerase largest subunit, were required for late gene expression. Furthermore, we found that LEF-8 and LEF-9 interacted in coimmunoprecipitation experiments. We determined possible interactions of all the RNA polymerase subunits in pairwise combinations and found associations between LEF-9 and P47, LEF-4 and P47, and LEF-8 and P47. In contrast, LEF-4 and LEF-8 did not coimmunoprecipitate but coimmunoprecipitated in the presence of P47, suggesting that they do not associate directly. A weak association was observed between LEF-4 and LEF-9. Further analysis also suggested that LEF-8, LEF-9, and P47 have the ability to self-associate. Studies on protein-protein interactions may provide insight into the structural design of the complex and mechanistic aspects affecting late and very late gene expression.
authors.affiliation: Molecular, Cellular, and Developmental Biology Program, Division of Biology, 116 Ackert Hall, Kansas State University, Manhattan, KS 66506-4901, USA.
authors.forename: Erin A
authors.initials: EA
authors.lastname: Crouch
authors.forename: Leah T
authors.initials: LT
authors.lastname: Cox
authors.forename: Kristy G
authors.initials: KG
authors.lastname: Morales
authors.forename: A Lorena
authors.initials: AL
authors.lastname: Passarelli
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D007915:Lepidoptera / Q000821:virology; D017924:Nucleopolyhedroviruses / Q000201:enzymology* / Q000235:genetics; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D014764:Viral Proteins; C084398:late expression factor 4, baculovirus; C087702:late expression factor 8, Baculovirus; D012321:DNA-Directed RNA Polymerases