Specificity of baculovirus P6.9 basic DNA-binding proteins and critical role of the C terminus in virion formation.
The majority of double-stranded DNA (dsDNA) viruses infecting eukaryotic organisms use host- or virus-expressed histones or protamine-like proteins to condense their genomes. In contrast, members of the Baculoviridae family use a protamine-like protein named P6.9. The dephosphorylated form of P6.9 binds to DNA in a non-sequence-specific manner. By using a p6.9-null mutant of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), we demonstrate that P6.9 is not required for viral DNA replication but is essential for the production of infectious virus. Virion production was rescued by P6.9 homologs from a number of Alphabaculovirus species and one Gammabaculovirus species but not from the genus Betabaculovirus, comprising the granuloviruses, or by the P6.9 homolog VP15 from the unrelated white spot syndrome virus of shrimp. Mutational analyses demonstrated that AcMNPV P6.9 with a conserved 11-residue deletion of the C terminus was not capable of rescuing p6.9-null AcMNPV, while a chimeric Betabaculovirus P6.9 containing the P6.9 C-terminal region of an Alphabaculovirus strain was able to do so. This implies that the C terminus of baculovirus P6.9 contains sequence elements essential for virion formation. Such elements may possibly interact with species- or genus-specific domains of other nucleocapsid proteins during virus assembly.
Laboratory of Virology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, Netherlands.
Manli
M
Wang
Era
E
Tuladhar
Shu
S
Shen
Hualin
H
Wang
Monique M
MM
van Oers
Just M
JM
Vlak
Marcel
M
Westenberg
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017924:Nucleopolyhedroviruses / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017384:Sequence Deletion; D018411:Spodoptera; D014758:Viral Core Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014779:Virus Replication
C099697:Ac-p6.9 protein, Autographa californica nucleopolyhedrovirus; D004268:DNA-Binding Proteins; D014758:Viral Core Proteins