A functional interaction of E7 with B-Myb-MuvB complex promotes acute cooperative transcriptional activation of both S- and M-phase genes. (129 c)

Abstract

High-risk human papillomaviruses are causative agents of cervical cancer. Viral protein E7 is required to establish and maintain the pro-oncogenic phenotype in infected cells, but the molecular mechanisms by which E7 promotes carcinogenesis are only partially understood. Our transcriptome analyses in primary human fibroblasts transduced with the viral protein revealed that E7 activates a group of mitotic genes via the activator B-Myb-MuvB complex. We show that E7 interacts with the B-Myb, FoxM1 and LIN9 components of this activator complex, leading to cooperative transcriptional activation of mitotic genes in primary cells and E7 recruitment to the corresponding promoters. E7 interaction with LIN9 and FoxM1 depended on the LXCXE motif, which is also required for pocket protein interaction and degradation. Using E7 mutants for the degradation of pocket proteins but intact for the LXCXE motif, we demonstrate that E7 functional interaction with the B-Myb-MuvB complex and pocket protein degradation are two discrete functions of the viral protein that cooperate to promote acute transcriptional activation of mitotic genes. Transcriptional level of E7 in patient's cervical lesions at different stages of progression was shown to correlate with those of B-Myb and FoxM1 as well as other mitotic gene transcripts, thereby linking E7 with cellular proliferation and progression in cervical cancer in vivo. E7 thus can directly activate the transcriptional levels of cell cycle genes independently of pocket protein stability.

Role of WDHD1 in Human Papillomavirus-Mediated Oncogenesis Identified by Transcriptional Profiling of E7-Expressing Cells

“…B-Myb has been implicated in a positive regulatory role for Cdk1 expression (49,56). We and others have shown that E7 upregulates B-Myb expression (7,46). Moreover, downregulation of B-Myb-induced G 1 arrest in E7-expressing cells upon DNA damage has been described previously (59).…”

“…Nonetheless, several gene expression profiling studies have been conducted on HPV E7-expressing cells using microarray analysis. The cells employed included mouse cells, cervical cancer cell lines (C33A and CaSki), and PHKs (3,(5)(6)(7)90). However, there are major limitations with the DNA microarray approach, such as the relatively high background noise resulting from solution-based DNA probe hybridization as well as the limited scope of profiling analysis, which is confined by the DNA probe set.…”

“…Multiple lines of evidence suggest that B-Myb plays an important role in HPV-associated carcinogenesis (7,42,(69)(70)(71). We recently showed that HPV E7 is able to activate the B-Myb gene (42,44,45).…”

“…E7 from the high-risk HPV types can abrogate cell cycle checkpoints and induces genomic instability. Although several transcription profiling studies for E7 have been conducted using DNA microarray analysis (3,(5)(6)(7), the HPV E7 activities downstream from, or independent of, pRb responsible for deregulation of cell cycle and induction of genomic instability are not fully understood.…”

Stranglehold on the spindle assembly checkpoint: the human papillomavirus E2 protein provokes BUBR1-dependent aneuploidy

“…E7 has been shown to enhance BUBR1 transcription by about 2.6 times when compared to GFP in primary fibroblasts using microarray experiments, 23 and accordingly to this result, the levels of BUBR1 were shown to be high in human foreskin fibroblasts stably expressing E7. 24 Interestingly, in synchronized HeLa cells released from G1/S transition for 6 hours (therefore around 4-6 hours before mitotic entry), the levels of BUBR1 were lower in cells expressing GFP-E2 and GFP-DTAD (which both repress E7) than in GFP-TAD and GFP-expressing cells (Fig.…”