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Molecular and Cellular Biology, May 1999, p. 3885-3894, Vol. 19, No. 5
Laboratory for Physiological Chemistry and
Centre for Biomedical Genetics,
Received 24 August 1998/Returned for modification 23 October
1998/Accepted 18 February 1999
Multiple adenovirus (Ad) early proteins have been shown to inhibit
transcription activation by p53 and thereby to alter its normal
biological functioning. Since these Ad proteins affect the activity of
p53 via different mechanisms, we examined whether this inhibition is
target gene specific. In addition, we analyzed whether the same Ad
early proteins have a comparable effect on transcription activation by
the recently identified p53 homologue p73. Our results show that the
large E1B proteins very efficiently inhibited the activity of p53 on
the Bax, p21Waf1, cyclin G, and MDM2 reporter constructs
but had no effect on the activation of the same reporter constructs by
p73, with the exception of some inhibition of the Bax promoter by Ad12
E1B. The repressive effect of the E1A proteins on p53 activity is less than that seen with the large E1B proteins, but the E1A proteins inhibit the activity of both p53 and p73. We could not detect significant inhibition of p53 functions by E4orf6, but a clear repression of the transcription activation by p73 by this Ad early protein was observed. In addition, we found that stable expression of
the Ad5 E1A and that of the E1B protein both caused increased p73
protein expression. The large E1B and the E4orf6 proteins together do
not target the p73 protein for rapid degradation after adenoviral
infection, as has previously been found for the p53 protein, probably
because the large E1B protein does not interact with p73. Our results
suggest that the p53 and p73 proteins are both inactivated after Ad
infection and transformation but via distinct mechanisms.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Distinct Regulation of p53 and p73 Activity by
Adenovirus E1A, E1B, and E4orf6 Proteins
*
Corresponding author. Mailing address: Laboratory for
Physiological Chemistry and Centre for Biomedical Genetics, Utrecht University, P.O. Box 80042, 3508 TA Utrecht, The Netherlands. Phone: 31 30 253 8961. Fax: 31 30 253 9035. E-mail:
W.T.Steegenga{at}med.uu.nl.
Molecular and Cellular Biology, May 1999, p. 3885-3894, Vol. 19, No. 5
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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