AMF-1/Gps2 Binds p300 and Enhances Its Interaction with Papillomavirus E2 Proteins

Abstract

The cellular protein AMF-1 (Gps2) positively modulates gene expression by the papillomavirus E2 protein (D. E. Breiding et al., Mol. Cell. Biol. 17:7208-7219, 1997). We show here that AMF-1 also binds the transcriptional coactivator p300 in vitro and in vivo. E2 interacted weakly with p300. These observations led to a model in which AMF-1 recruits p300 into a complex with E2. Cotransfection of AMF-1 or p300 stimulated levels of E2-dependent transcription, while cotransfection of both AMF-1 and p300 showed an additive effect. The functional significance of p300 recruitment for E2 transactivation was evidenced by repression of E2-activated transcription by adenovirus E1A, which inhibits both coactivator and acetylase activities of p300. Antibodies to AMF-1 or E2 immunoprecipitated histone acetylase activity from cell lysates. Western blotting using antibody against acetyl-lysine failed to detect acetylation of AMF-1 or E2 in complex with p300. These results suggest that AMF-1 facilitates the recruitment of p300 and its histone acetylase activity into complexes with E2 and represents a novel mechanism of transcriptional activation.The bovine papillomavirus type 1 (BPV-1) E2 protein serves multiple functions for the virus. Binding of its carboxy-terminal sequence-specific DNA binding domain (DBD) to recognition elements in the papillomavirus genome regulates viral gene expression and replication of the viral genome (1,5,8,16,19,57). The amino-terminal activation domain (AD) of E2 mediates protein-protein interactions with the cellular transcription machinery. This region also binds the papillomavirus E1 protein, a DNA binding helicase essential for viral DNA replication (17, 27, 54). E2 targets E1 to the origin of replication. It is also believed that E2 plays an additional role in DNA replication, as several E2 mutants retained E1 and DNA binding were unable to stimulate replication (16). Because E2 is required for replication of viral nucleosomal DNA but not naked plasmid DNA in vitro (33,53), it has been proposed that E2 may relieve chromatin suppression and allowing entry of cellular replication and transcription factors to the origin and promoter, respectively.The cooperation of at least two functional units within the large 220-amino-acid E2 AD is essential for transcriptional activation. The crystal structure of the human papillomavirus (HPV) E2 AD reveals multiple surfaces available for proteinprotein interactions (2, 25). A transcription factor IIB (TFIIB)

Involvement of corepressor complex subunit GPS2 in transcriptional pathways governing human bile acid biosynthesis

“…1B and SI Fig. 7 D and E), consistent with previously suggested connections to N-CoR and p300 (16)(17)(18)(19).…”

“…Such differential regulation is compatible with a dual activator/ repressor function of GPS2 observed by us (see above) and in previous studies: In addition to representing a subunit of the N-CoR complex (16)(17)(18), GPS2 can potentiate papilloma virus E2 and p53 transactivity by recruiting the histone acetyltransferase p300 (19,25).…”

“…1B and SI Fig. 7 D and E), consistent with previously suggested connections to N-CoR and p300 (16)(17)(18)(19).Next, the putative role of endogenous GPS2 in transcriptional repression by SHP was investigated in a unique repressor assay (20) combined with RNA interference (Fig. 1C).…”

Viral epigenomes in human tumorigenesis

“…Apart from methylation changes in this virus genome, other epigenetic changes might occur through direct interactions between HPV proteins (E2, E7) and cell proteins involved in DNA methylation (DNMT1) (Burgers et al, 2006), or through processes related to the chromatin remodeling machinery (CBP, pCAF, p300, Mi2b) (Brehm et al, 1999;Patel et al, 1999;Lee et al, 2000;Peng et al, 2000;Avvakumov et al, 2003;Bernat et al, 2003), eventually modifying the normal epigenetic processes in the host.…”

The Human Papillomavirus E6 protein and its contribution to malignant progression

“…Thus, the HPV major transcriptional activator, E2, also interacts with p300/CBP (Lee et al, 2000a;Marcello et al, 2000). This appears to involve a cellular protein, AMF-1/Gps2, which in turn enhances p300 activity but which, intriguingly, is also a target for E6 mediated degradation (Peng et al, 2000;Degenhardt and Silverstein, 2001). Therefore the interaction between E6 and p300 may represent a means of downregulating E2 transcriptional activity, and thereby controlling the levels of E6 expression by a feed-back mechanism.…”