Distinct modulation of p53 activity in transcription and cell-cycle regulation by the large (54 kDa) and small (21 kDa) adenovirus E1B proteins.
P53 can both stimulate transcription via the p53-consensus sequence as well as inhibit gene expression via CAAT-TATA-sequences. Certain viral and cellular proteins can abrogate the p53-dependent stimulation of transcription by physical association. In addition, it has been shown that the large E1B protein of adenovirus type 12 (Ad12), E1B/54 kDa, can block the transcription activation potential of p53, without binding to p53. Here we show that this E1B/54-kDa protein also can prevent the repression of transcription of transfected and endogenous p53 in transient transfections. In cells containing wild-type p53 but stably expressing high levels of E1B/54 kDa, no induction of WAF1 mRNA after X-ray irradiation could be detected. In contrast, expression of another non-p53 binding E1B protein, Ad5 E1B/21 kDa has no effect on WAF-1 expression. Results of an electromobility shift assay indicated that the abrogation of p53-mediated transcription activation by E1B/54 kDa cannot be explained by inhibition of the DNA-binding capacity of p53. A biological consequence of expression of E1B/54 kDa is the loss of G1 cell-cycle arrest after X-ray irradiation, while cells expressing the E1B/21 kDa still arrest in G1 after DNA damage.
Steegenga
W T
WT
Laboratory of Molecular Carcinogenesis, Sylvius Laboratories, Leiden University, The Netherlands.
Van Laar
T
T
Shvarts
A
A
Terleth
C
C
Van der Eb
A J
AJ
Jochemsen
A G
AG
D017501:Adenovirus E1B Proteins / Q000502:physiology*; D000260:Adenoviruses, Human / Q000737:chemistry; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D016193:G1 Phase; D005786:Gene Expression Regulation / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D014158:Transcription, Genetic / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
D017501:Adenovirus E1B Proteins; C493956:CDKN1A protein, human; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D004247:DNA