Induction of apoptosis in Saccharomyces cerevisiae results in the spontaneous maturation of tetravirus procapsids in vivo.
The Tetraviridae are a family of small, non-enveloped, insect RNA viruses consisting of one or two single-stranded, positive-sense genomic RNAs encapsidated in an icosahedral capsid with T=4 symmetry. Tetravirus procapsids undergo maturation when exposed to a low pH environment in vitro. While the structural biology of the conformational changes that mediate acid-dependent maturation is well understood, little is known about the significance of acid-dependent maturation in vivo. To address this question, the capsid-coding sequence of the tetravirus Helicoverpa armigera stunt virus was expressed in Saccharomyces cerevisiae cells. Virus-like particles were shown to assemble as procapsids that matured spontaneously in vivo as the cells began to age. Growth in the presence of hydrogen peroxide or acetic acid, which induced apoptosis or programmed cell death in the yeast cells, resulted in virus-like particle maturation. The results demonstrate that assembly-dependent maturation of tetravirus procapsids in vivo is linked to the onset of apoptosis in yeast cells. We propose that the reduction in pH required for tetraviral maturation may be the result of cytosolic acidification, which is associated with the early onset of programmed cell death in infected cells.
Tomasicchio
Michele
M
Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
Venter
Philip Arno
PA
Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
H J Gordon
Karl
K
CSIRO Entomology, Box 1700, Canberra, ACT 2601, Australia.
N Hanzlik
Terry
T
CSIRO Entomology, Box 1700, Canberra, ACT 2601, Australia.
Dorrington
Rosemary Ann
RA
Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa.
D017209:Apoptosis; D015967:Gene Expression Regulation, Viral; D020287:In Situ Nick-End Labeling; D007304:Insect Viruses / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D012328:RNA Viruses / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology / Q000821:virology*