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J. Virol., 09 1995, 5311-5319, Vol 69, No. 9
A Wistuba, S Weger, A Kern and JA Kleinschmidt
The proteins encoded by the adeno-associated virus type 2 (AAV-2) rep and
cap genes obtained during a productive infection of HeLa cells with AAV-2
and adenovirus type 2 were fractionated according to solubility, cellular
localization, and sedimentation properties. The majority of Rep and Cap
proteins accumulated in the nucleus, where they distributed into a soluble
and an insoluble fraction. Analysis of the soluble nuclear fraction of
capsid proteins by sucrose density gradients showed that they formed at
least three steady-state pools: a monomer pool sedimenting at about 6S, a
pool of oligomeric intermediates sedimenting between 10 and 15S, and a
broad pool of assembly products with a peak between 60 and 110S, the known
sedimentation positions of empty and full capsids. While the soluble
nuclear monomer and oligomer pool contained predominantly only two capsid
proteins, the 30 to 180S assembly products contained VP1, VP2, and VP3 in a
stoichiometry similar to that of purified virions. They probably represent
different intermediates in capsid assembly, DNA encapsidation, and capsid
maturation. In contrast, the cytoplasmic fraction of capsid proteins showed
a pattern of oligomers continuously increasing in size without a defined
peak, suggesting that assembly of 60S particles occurs in the nucleus.
Soluble nuclear Rep proteins were distributed over the whole sedimentation
range, probably as a result of association with AAV DNA. Subfractions of
the Rep proteins with defined sedimentation values were obtained in the
soluble nuclear and cytoplasmic fractions. We were able to
coimmunoprecipitate capsid proteins sedimenting between 60 and 110S with
antibodies against Rep proteins, suggesting that they exist in common
complexes possibly involved in AAV DNA packaging. Antibodies against the
capsid proteins, however, precipitated Rep78 and Rep68 predominantly with a
peak around 30S representing a second complex containing Rep and Cap
proteins.
Copyright © 1995, American Society for Microbiology
Intermediates of adeno-associated virus type 2 assembly: identification of soluble complexes containing Rep and Cap proteins
Deutsches Krebsforschungszentrum, Forschungsschwerpunkt Angewandte Tumorvirologie, Heidelberg, Germany.
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