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Journal of Virology, June 2001, p. 5197-5204, Vol. 75, No. 11
Department of
Pathology1 and The Fearing Laboratory
and The Division of Reproductive Endocrinology and Fertility,
Department of Obstetrics, Gynecology, and Reproductive Biology, Brigham
and Women's Hospital,2 Harvard Medical
School, Boston, Massachusetts 02115
Received 24 January 2001/Accepted 12 March 2001
The human cytomegalovirus-encoded US2 glycoprotein targets
endoplasmic reticulum-resident major histocompatibility complex (MHC)
class I heavy chains for rapid degradation by the proteasome. We
demonstrate that the endoplasmic reticulum-lumenal domain of US2 allows
tight interaction with class I molecules encoded by the HLA-A locus.
Recombinant soluble US2 binds properly folded, peptide-containing
recombinant HLA-A2 molecules in a peptide sequence-independent manner,
consistent with US2's ability to broadly downregulate class I
molecules. The physicochemical properties of the US2/MHC class I
complex suggest a 1:1 stoichiometry. These results demonstrate that US2
does not require additional cellular proteins to specifically interact
with soluble class I molecules. Binding of US2 does not significantly
alter the conformation of class I molecules, as a soluble T-cell
receptor can simultaneously recognize class I molecules associated with
US2. The lumenal domain of US2 can differentiate between the products
of distinct class I loci, as US2 binds several HLA-A locus products
while being unable to bind recombinant HLA-B7, HLA-B27, HLA-Cw4, or
HLA-E. We did not observe interaction between soluble US2 and either
recombinant HLA-DR1 or recombinant HLA-DM. The substrate specificity of
US2 may help explain the presence in human cytomegalovirus of multiple
strategies for downregulation of MHC class I molecules.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.11.5197-5204.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Human Cytomegalovirus US2 Endoplasmic
Reticulum-Lumenal Domain Dictates Association with Major
Histocompatibility Complex Class I in a Locus-Specific Manner
*
Corresponding author. Mailing address: Department of
Pathology, Harvard Medical School, Building D2, Room 137, 200 Longwood Ave., Boston, MA 02115. Phone: (617) 432-4776. Fax: (617) 432-4775. E-mail: ploegh{at}hms.harvard.edu.
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