The putative metal coordination motif in the endonuclease domain of human Parvovirus B19 NS1 is critical for NS1 induced S phase arrest and DNA damage.
The non-structural proteins (NS) of the parvovirus family are highly conserved multi-functional molecules that have been extensively characterized and shown to be integral to viral replication. Along with NTP-dependent helicase activity, these proteins carry within their sequences domains that allow them to bind DNA and act as nucleases in order to resolve the concatameric intermediates developed during viral replication. The parvovirus B19 NS1 protein contains sequence domains highly similar to those previously implicated in the above-described functions of NS proteins from adeno-associated virus (AAV), minute virus of mice (MVM) and other non-human parvoviruses. Previous studies have shown that transient transfection of B19 NS1 into human liver carcinoma (HepG2) cells initiates the intrinsic apoptotic cascade, ultimately resulting in cell death. In an effort to elucidate the mechanism of mammalian cell demise in the presence of B19 NS1, we undertook a mutagenesis analysis of the protein's endonuclease domain. Our studies have shown that, unlike wild-type NS1, which induces an accumulation of DNA damage, S phase arrest and apoptosis in HepG2 cells, disruptions in the metal coordination motif of the B19 NS1 protein reduce its ability to induce DNA damage and to trigger S phase arrest and subsequent apoptosis. These studies support our hypothesis that, in the absence of replicating B19 genomes, NS1-induced host cell DNA damage is responsible for apoptotic cell death observed in parvoviral infection of non-permissive mammalian cells.
Pennsylvania State College of Medicine/ Milton S. Hershey Medical Center, Hershey, PA, USA.
Violetta
V
Kivovich
Leona
L
Gilbert
Matti
M
Vuento
Stanley J
SJ
Naides
D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis; D004249:DNA Damage; D004252:DNA Mutational Analysis; D004720:Endonucleases / Q000737:chemistry* / Q000502:physiology; D056945:Hep G2 Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D016732:Parvovirus B19, Human / Q000502:physiology*; D059807:S Phase Cell Cycle Checkpoints; D018411:Spodoptera; D017361:Viral Nonstructural Proteins / Q000032:analysis / Q000737:chemistry* / Q000502:physiology; D014779:Virus Replication
C106202:NS1 protein, parvovirus; D017361:Viral Nonstructural Proteins; D004720:Endonucleases