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Journal of Virology, January 2000, p. 899-913, Vol. 74, No. 2
Department of Biochemistry, University of
Medicine and Dentistry of New Jersey
Received 13 November 1998/Accepted 29 September 1999
Chimeras were previously generated between the ecotropic
(Moloney-MuLV) and amphotropic (4070A) SU and TM proteins of murine leukemia virus (MuLV). After passage in D17 cells, three chimeras with
junctions in the C terminus of SU (AE5, AE6, and AE7), showed improved
kinetics of viral spreading, suggesting that they had adapted.
Sequencing of the viruses derived from the D17 cell lines revealed
second-site changes within the env gene. Changes were detected in the receptor binding domain, the proline-rich region, the C
terminus of SU, and the ectodomain of TM. Second-site changes were
subcloned into the parental DNA, singly and in combination, and tested
for viability. All viruses had maintained their original cloned
mutations and junctions. Reconstruction and passage of AE7 or AE6 virus
with single point mutations recovered the additional second-site
changes identified in the parental population. The AE5 isolate required
changes in the VRA, the VRC, the VRB-hinge region, and the C terminus
of SU for efficient infection. Passage of virus, including the parental
4070A, in D17 cells resulted in a predominant G100R mutation within the
receptor binding domain. Viruses were subjected to titer determination
in three cell types, NIH 3T3, canine D17, and 293T. AE6 viruses with
changes in the proline-rich region initially adapted for growth on D17
cells could infect all cell types tested. AE6-based chimeras with
additional mutations in the C terminus of SU could infect D17 and 293T
cells. Infection of NIH 3T3 cells was dependent on the proline-rich
mutation. AE7-based chimeras encoding L538Q and G100R were impaired in
infecting NIH 3T3 and 293T cells.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Second-Site Changes Affect Viability of
Amphotropic/Ecotropic Chimeric Enveloped Murine Leukemia
Viruses
Robert Wood Johnson Medical
School, Piscataway, New Jersey 08854
*
Corresponding author. Mailing address: Department of
Biochemistry, University of Medicine and Dentistry of New
Jersey
Robert Wood Johnson Medical School, 675 Hoes Ln., Piscataway,
NJ 08854. Phone: (732) 235-5048. Fax: (732) 235-4783; E-mail:
Roth{at}waksman.rutgers.edu.
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