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  • Title: SV40 large T antigen transactivates the human cdc2 promoter by inducing a CCAAT box binding factor.
    Author: Chen H, Campisi J, Padmanabhan R.
    Journal: J Biol Chem; 1996 Jun 14; 271(24):13959-67. PubMed ID: 8662914.
    Abstract:
    Cyclin-dependent protein kinases (Cdks) play a key role in the cell division cycle of eukaryotic cells. Cdc2, the first mammalian Cdk that was discovered, is expressed in S phase and functions in the G2 to M phase transition. By transfecting segments of the human cdc2 promoter linked to a reporter gene into monkey kidney (CV-1) cells, we identified the region containing the Sp1, E2F, and two CCAAT box binding sites as essential and sufficient for basal transcription. SV40 large T antigen (SV40-LT) is a viral oncoprotein that transactivates viral and cellular promoters and induces DNA synthesis in quiescent cells. SV40-LT transactivated wild-type cdc2 promoter/reporter constructs in a dose-dependent manner, coinciding with an increase in endogenous cdc2 mRNA. A mutant promoter from which the two CCAAT box motifs were deleted was 8-fold less sensitive to SV40-LT. Activation by SV40-LT did not require its ability to bind the retinoblastoma or p53 tumor suppressor proteins. SV40-LT induced a specific CCAAT box-binding factor (CBF) in CV-1 and COS-7 cells, as judged by gel shift and Southwestern analyses. Similar results were obtained in human fibroblasts expressing a conditional SV40-LT. The SV40-LT-inducible CBF appears to be novel and differs from the CBF that activates heat shock protein 70 gene expression.
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