Direct Interaction between Nucleosome Assembly Protein 1 and the Papillomavirus E2 Proteins Involved in Activation of Transcription

Abstract

Using a yeast two-hybrid screen, we identified human nucleosome assembly protein 1 (hNAP-1) as a protein interacting with the activation domain of the transcriptional activator encoded by papillomaviruses (PVs), the E2 protein. We show that the interaction between E2 and hNAP-1 is direct and not merely mediated by the transcriptional coactivator p300, which is bound by both proteins. Coexpression of hNAP-1 strongly enhances activation by E2, indicating a functional interaction as well. E2 binds to at least two separate domains within hNAP-1, one within the C terminus and an internal domain. The binding of E2 to hNAP-1 is necessary for cooperativity between the factors. Moreover, the N-terminal 91 amino acids are crucial for the transcriptional activity of hNAP-1, since deletion mutants lacking this N-terminal portion fail to cooperate with E2. We provide evidence that hNAP-1, E2, and p300 can form a ternary complex efficient in the activation of transcription. We also show that p53 directly interacts with hNAP-1, indicating that transcriptional activators in addition to PV E2 interact with hNAP-1. These results suggest that the binding of sequence-specific DNA binding proteins to hNAP-1 may be an important step contributing to the activation of transcription.

We thank Y. Ishimi for the gift of the monoclonal antibody against hNAP-1, D. Livingston and M. Scheffner for providing plasmid DNAs, and P. Bartel for providing yeast strain YM954. We also thank Herbert Pfister and Andrew Barker for critical reading of the manuscript and Karin Schnetz for helpful support.

This work was supported by the Deutsche Forschungsgemeinschaft (SFB274-A8, STE604/3-1, and STE604/3-2) and by the BMBF (Aktenzeichen 0312708F). G.S. was the recipient of a Lise-Meitner Habilitationsstipendium.