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Journal of Virology, April 1999, p. 2825-2831, Vol. 73, No. 4
Department of Microbiology, Cancer Center,
University of Pennsylvania, Philadelphia, Pennsylvania 19104-6142
Received 10 September 1998/Accepted 14 December 1998
The major immediate-early (MIE) gene of human cytomegalovirus
(HCMV) encodes several MIE proteins (MIEPs) produced as a result of
alternative splicing and polyadenylation of the primary transcript. Previously we demonstrated that the HCMV MIEPs expressed from the
entire MIE gene could rescue the temperature-sensitive (ts) transcriptional defect in the ts13 cell line. This defect
is caused by a ts mutation in TAFII250, the
250-kDa TATA binding protein-associated factor (TAF). These and other
data suggested that the MIEPs perform a TAF-like function in complex
with the basal transcription factor TFIID. In addition to the
transcriptional defect, the ts mutation in ts13
cells results in a defect in cell cycle progression which ultimately
leads to apoptosis. Since all of these defects can be rescued by
wild-type TAFII250, we asked whether the MIEPs could rescue
the cell cycle defect and/or affect the progression to apoptosis. We
have found that the MIEPs, expressed from the entire MIE gene, do not
rescue the cell cycle block in ts13 cells grown at the
nonpermissive temperature. However, despite the maintenance of the cell
cycle block, the ts13 cells which express the MIEPs are
resistant to apoptosis. MIEP mutants, which have previously been shown
to be defective in rescuing the ts transcriptional defect,
maintained the ability to inhibit apoptosis. Hence, the MIEP functions
which affect transcription appear to be separable from the functions
which inhibit apoptosis. We discuss these data in the light of the HCMV
life cycle and the possibility that the MIEPs promote cellular
transformation by a "hit-and-run" mechanism.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Effects of Human Cytomegalovirus Major Immediate-Early Proteins
in Controlling the Cell Cycle and Inhibiting Apoptosis: Studies
with ts13 Cells
and
*
Corresponding author. Mailing address: University of
Pennsylvania, 560 Clinical Research Building, 415 Curie Blvd.,
Philadelphia, PA 19104-6142. Phone: (215) 898-3256. Fax: (215)
573-3888. E-mail: alwine{at}mail.med.upenn.edu.
Present address: Dept. of Microbiology and Immunology and Howard
Hughes Medical Institute, University of California San Francisco, San
Francisco, CA 94143.
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