Role of the CCAAT -binding protein CBF in cell cycle regulation

Qianghua Hu, The University of Texas School of Public Health


Transcription factors generally refer to proteins that bind DNA at a promoter or enhahcer region or site, where they regulate transcription and by which play important roles in maintaining normal functions of the cell. One of them, CBF, is a transcription factor that binds to a CCAAT motif/box present in 30-60% of eukaryotic RNA polymerase II promoters. CBF consists of three subunits, CBF-A, CBF-B, and CBF-C. Previous studies showed that binding of the CBF transcription factor to cellular promoters is essential for cell proliferation. This observation prompted us to investigate the function of CBF in relation to cell cycle progression and in cell-cycle-regulated transcription. In this study, we used a tetracycline-inducible adenoviral vector to express Bdbd, a truncated CBF-B subunit lacking a transcription activation domain, in various mammalian cell lines. The Bdbd polypeptide interacts with cellular CBF-A/CBF-C and binds to promoters containing CBF binding sites. Interestingly, expression of Bdbd in various mammalian cells resulted in inhibition of cell proliferation and specific cell cycle arrest at G2/M phase. Gene expression analysis demonstrated that expression of Bdbd strongly suppressed cell cycle dependent transcription activation of Cyclin B1, Aurora A, and CDC2 genes, which are key regulators for cell cycle progression at G2/M phase. Chromatin immunoprecipitation analysis showed that Bdbd significantly inhibited binding of TATA-binding protein, TBP to both Cyclin B1 and Aurora A promoters, but did not inhibit binding of E2F3 activator to Cyclin B1 promoter. Cell death assays indicated that Bdbd expression did not result in apoptosis but caused slight necrosis. In summary, this study showed that the activation domain of CBF-B plays an essential role in transcription activation of Cyclin B1 and Aurora A genes at G2/M phase, thus regulating cell cycle progression at G2/M phase. Mutations of transcription factors have been widely associated with human diseases. In the long term, this study will help lead to new therapeutics for proliferative diseases, such as cancers and tumors, which are of great public health concern.

Subject Area

Molecular biology|Cellular biology

Recommended Citation

Hu, Qianghua, "Role of the CCAAT -binding protein CBF in cell cycle regulation" (2006). Texas Medical Center Dissertations (via ProQuest). AAI3241396.