A. Bermingham et Pl. Collins, The M2-2 protein of human respiratory syncytial virus is a regulatory factor involved in the balance between RNA replication and transcription, P NAS US, 96(20), 1999, pp. 11259-11264
Citations number
29
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
The M2 mRNA of human respiratory syncytial virus (RSV) contains two overlap
ping ORFs, encoding the transcription antitermination protein (M2-1) and th
e 90-aa M2-2 protein of unknown function. Viable recombinant RSV was recove
red in which expression of M2-2 was ablated, identifying it as an accessory
factor dispensable for growth in vitro. Virus lacking M2-2 grew less effic
iently than did the wild-type parent in vitro, with titers that were reduce
d 1,000-fold during the initial 2-5 days and 10-fold by days 7-8. Compared
with wild-type virus, the intracellular accumulation of RNA by M2-2 knockou
t virus was reduced 3- to 4-fold or more for genomic RNA and increased 2- t
o 4-fold or more for mRNA, Synthesis of the F and G glycoproteins, the majo
r RSV neutralization and protective antigens, was increased in proportion w
ith that of mRNA. In cells infected with wild-type RSV, mRNA accumulation i
ncreased dramatically up to ap proximately 12-15 hr after infection and the
n leveled off, whereas accumulation continued to increase in cells infected
with the M2-2 knockout viruses. These findings suggest that M2-2 mediates
a regulatory "switch" from transcription to RNA replication, one that provi
des an initial high level of mRNA synthesis followed by a shift in the RNA
synthetic program in favor of genomic RNA for virion assembly. With regard
to vaccine development, the M2-2 knockout has a highly desirable phenotype
in which virus growth is attenuated while gene expression is concomitantly
increased.