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.

Chromatin-Specific Remodeling by HMGB1 and Linker Histone H1 Silences Proinflammatory Genes during Endotoxin Tolerance

“…Temporary release of H1 from TNF-␣ nucleosomal DNA may allow chromatin decondensation, which would reopen the gate for genespecific transcription factor to bind. One such opening factor could be the nucleosome assembly protein NAP1, which is implicated in the regulation of transcription factor binding to chromatin and augmenting the activity of many p300 target genes, including p53 and E2F (39,44). We find that removal of HMGB1 and reduction in RelB binding results in binding of NAP1 (which we detected in responsive cells only) to the TNF-␣ promoter in silenced cells (data not shown).…”

Cytoplasmic localization of DGKζ exerts a protective effect against p53-mediated cytotoxicity

“…NAP is a highly conserved histone chaperone protein that is involved in the dynamic regulation of the H2A-H2B histone heterodimer (Zlatanova et al, 2007). Furthermore, NAP1 is shown to interact functionally with the transcriptional activator E2 together with p300, the transcriptional co-activator possessing histone acetyltransferase activity, suggesting a direct contribution of NAP1 in the regulation of the transcriptional machinery (Rehtanz et al, 2004). In the present study, we provide evidence that an anti-apoptotic effect of NAP1Ls is mediated through DGKf cytoplasmic translocation, which proposes a potential novel role of NAP under stress conditions.…”

Nucleosome Assembly Protein 1 Exchanges Histone H2A-H2B Dimers and Assists Nucleosome Sliding

“…NAP-1 and other acidic histone chaperones were also shown to cooperate with SWI/SNF complexes in chromatin remodeling and to facilitate transcription factor binding to nucleosomal DNA in vitro (24 -26). Furthermore, direct functional and physical interactions between transcriptional activators and human NAP-1 were reported (27)(28)(29). Systematic deletion of the NAP-1 gene in yeast had no pronounced effect on yeast cells (30), suggesting redundancy in its function.…”