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Molecular and Cellular Biology, September 1998, p. 5219-5228, Vol. 18, No. 9
Department of Microbiology and Molecular
Genetics1 and
Department of
Immunology,2 New England Regional Primate
Research Center, Harvard Medical School, Southborough, Massachusetts
01772
Received 14 January 1998/Returned for modification 23 March
1998/Accepted 12 June 1998
Kaposi's sarcoma-associated herpesvirus (KSHV) is consistently
identified in Kaposi's sarcoma and body cavity-based lymphoma. KSHV
encodes a transforming protein called K1 which is structurally similar
to lymphocyte receptors. We have found that a highly conserved region
of the cytoplasmic domain of K1 resembles the sequence of
immunoreceptor tyrosine-based activation motifs (ITAMs). To demonstrate
the signal-transducing activity of K1, we constructed a chimeric
protein in which the cytoplasmic tail of the human CD8
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Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of an Immunoreceptor Tyrosine-Based
Activation Motif of K1 Transforming Protein of Kaposi's
Sarcoma-Associated Herpesvirus
polypeptide
was replaced with that of KSHV K1. Expression of the CD8-K1 chimera in
B cells induced cellular tyrosine phosphorylation and intracellular
calcium mobilization upon stimulation with an anti-CD8 antibody.
Mutational analyses showed that the putative ITAM of K1 was required
for its signal-transducing activity. Furthermore, tyrosine residues of
the putative ITAM of K1 were phosphorylated upon stimulation, and this
allowed subsequent binding of SH2-containing proteins. These results
demonstrate that the KSHV transforming protein K1 contains a functional
ITAM in its cytoplasmic domain and that it can transduce signals to
induce cellular activation.
*
Corresponding author. Mailing address: New England
Regional Primate Research Center, 1 Pine Hill Dr., Southborough, MA
01772. Phone: (508) 624-8083. Fax: (508) 624-8190. E-mail:
jjung{at}warren.med.harvard.edu.
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