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J. Virol., 07 1996, 4299-4310, Vol 70, No. 7
J Colgan, HE Yuan, EK Franke and J Luban
The cellular peptidyl-prolyl isomerase cyclophilin A (CyPA) is incorporated
into human immunodeficiency virus type 1 (HIV-1) virions via direct
contacts with the HIV-1 Gag polyprotein. Disruption of the Gag-CyPA
interaction leads to the production of HIV-1 particles lacking CyPA; these
virions are noninfectious, indicating that contacts between CyPA and Gag
are necessary for HIV-1 replication. Here, we have used the yeast
two-hybrid system in conjunction with an in vitro binding assay to identify
the minimal domain of Gag required for binding to CyPA. Analysis of a panel
of gag deletion mutants in the two-hybrid system indicated that a region
spanning the central portion of the capsid (CA) domain was sufficient for
interactions with CyPA, but discrepancies between results obtained in
different fusion protein contexts suggested that multimerization of Gag
might also be necessary for binding to CyPA. Consistent with a requirement
for multimerization, the binding of Gag to CyPA in vitro required a region
within the nucleocapsid (NC) domain shown previously to be important for
Gag self- association. Substitution of a heterologous dimerization motif
for the region from NC also promoted specific binding to CyPA, confirming
that interactions with CyPA are dependent on Gag multimerization. Fusion of
the heterologous dimerization motif to a 100-amino-acid domain from CA was
sufficient for binding to CyPA in vitro. These results define the minimal
CyPA-binding domain within Gag and provide insight into the mechanism by
which CyPA is incorporated into HIV-1 virions.
Copyright © 1996, American Society for Microbiology
Binding of the human immunodeficiency virus type 1 Gag polyprotein to cyclophilin A is mediated by the central region of capsid and requires Gag dimerization
Department of Microbiology, College of Physicians and Surgeons of Columbia University, New York, New York 10032USA.
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