Borna disease virus matrix protein is an integral component of the viral ribonucleoprotein complex that does not interfere with polymerase activity.
We have recently shown that the matrix protein M of Borna disease virus (BDV) copurifies with the affinity-purified nucleoprotein (N) from BDV-infected cells, suggesting that M is an integral component of the viral ribonucleoprotein complex (RNP). However, further studies were hampered by the lack of appropriate tools. Here we generated an M-specific rabbit polyclonal antiserum to investigate the intracellular distribution of M as well as its colocalization with other viral proteins in BDV-infected cells. Immunofluorescence analysis revealed that M is located both in the cytoplasm and in nuclear punctate structures typical for BDV infection. Colocalization studies indicated an association of M with nucleocapsid proteins in these nuclear punctate structures. In situ hybridization analysis revealed that M also colocalizes with the viral genome, implying that M associates directly with viral RNPs. Biochemical studies demonstrated that M binds specifically to the phosphoprotein P but not to N. Binding of M to P involves the N terminus of P and is independent of the ability of P to oligomerize. Surprisingly, despite P-M complex formation, BDV polymerase activity was not inhibited but rather slightly elevated by M, as revealed in a minireplicon assay. Thus, unlike M proteins of other negative-strand RNA viruses, BDV-M seems to be an integral component of the RNPs without interfering with the viral polymerase activity. We propose that this unique feature of BDV-M is a prerequisite for the establishment of BDV persistence.
Chase
Geoffrey
G
Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, Freiburg, Germany.
Mayer
Daniel
D
Hildebrand
Antonia
A
Frank
Ronald
R
Hayashi
Yohei
Y
Tomonaga
Keizo
K
Schwemmle
Martin
M
D000818:Animals; D001891:Borna disease virus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D002460:Cell Line; D002522:Chlorocebus aethiops; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry*; D013347:Subcellular Fractions / Q000378:metabolism; D014709:Vero Cells; D014763:Viral Matrix Proteins / Q000032:analysis / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D010750:Phosphoproteins; D012261:Ribonucleoproteins; D014763:Viral Matrix Proteins; D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases