The myxoma virus M-T4 gene encodes a novel RDEL-containing protein that is retained within the endoplasmic reticulum and is important for the productive infection of lymphocytes.
To investigate the contribution of the myxoma virus M-T4 gene to viral virulence, both copies of the M-T4 gene were inactivated by disruption and insertion of the Escherichia coli guanosine phosphoribosyltransferase gene. Infection of European rabbits with the recombinant M-T4-deleted virus, vMyxlacT4, resulted in disease attenuation. In contrast, infection of rabbits with vMyxlac elicited the classical features of lethal myxomatosis. A notable decrease in the number of secondary lesions in animals infected with vMyxlacT4 suggested an inability of the virus to disseminate in vivo. Infection of either a rabbit CD4+ T cell line, RL-5, or primary rabbit peripheral blood lymphocytes with vMyxlacT4- resulted in the rapid induction of apoptosis. Sequence analysis of M-T4 revealed both an N-terminal signal sequence and a C-terminal -RDEL sequence, suggesting that M-T4 resides in the endoplasmic reticulum. The M-T4 protein was found to be sensitive to endo H digestion and confocal fluorescence microscopy demonstrated that M-T4 colocalized with calreticulin, indicating that M-T4 is retained within the endoplasmic reticulum. Our results indicate that M-T4 is the first example of an intracellular virulence factor in myxoma virus that functions from within the endoplasmic reticulum and is necessary for the productive infection of lymphocytes.
Barry
M
M
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Hnatiuk
S
S
Mossman
K
K
Lee
S F
SF
Boshkov
L
L
McFadden
G
G
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D002460:Cell Line; D003673:Defective Viruses / Q000235:genetics / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D005814:Genes, Viral; D008214:Lymphocytes / Q000821:virology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009233:Myxoma virus / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity / Q000502:physiology; D009234:Myxomatosis, Infectious / Q000276:immunology / Q000821:virology; D011817:Rabbits; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology; D015678:Viral Structural Proteins / Q000235:genetics; D014774:Virulence / Q000235:genetics; D014779:Virus Replication
C110150:M-T4 protein, myxoma virus; D014764:Viral Proteins; D015678:Viral Structural Proteins