Specific in vitro interaction between papillomavirus E2 proteins and TBP-associated factors

The bovine and human papillomavirus (BPV/HPV) E2 proteins bind specifically to palindromic sequences ACCGN4CGGT that are concentrated within the viral long control region, where they regulate viral oncogene transcription. E2 can activate viral promoters over relatively large distances within the viral genome and was shown to cooperate with a number of cellular transcription factors. Transcriptional activator proteins, such as E2, are thought to act, at least in part, by influencing the assembly and/or stability of preinitiation complexes and it has been suggested that the transcription factor IID, composed by the TATA-binding protein (TBP) and numerous TBP-associated factors (TAFs), is a possible target of this important viral protein. In this paper, we demonstrate that E2 proteins associate in vitro with several TAFs, in particular with TAFII250 and TAFII80. In addition, we observed that the association of TAFII250 with BPV1 E2 is stronger than with HPV18 E2 and that the carboxy terminal domain of both viral proteins is involved in this interaction. On the other hand, TAFII80 binds with similar strength to both E2 proteins through their amino terminal region. These observations may help to explain the different behavior of bovine and human E2 proteins, since BPV E2 is a stronger transcriptional activator than HPV18 E2.