RNA splicing factors regulated by HPV16 during cervical tumour progression

Abstract

The most prevalent human papillomaviruses (HPVs) causing cervical disease are the 'high-risk' HPV types 16 and 18. All papillomaviruses express a transcription factor, E2, that can regulate viral and cellular gene expression. Recently, we demonstrated high-risk HPV E2-mediated transcriptional transactivation of SF2/ASF. This essential oncoprotein is a key member of a family of proteins, the SR proteins, that regulate constitutive and alternative splicing. Tight control of RNA splicing is necessary for the production of wild-type proteins. So, aberrant expression of SR proteins is involved in the aetiology of a range of human diseases, including cancer. Here we demonstrate epithelial differentiation-specific control of SF2/ASF in HPV16-infected keratinocytes in organotypic raft culture and in low-grade cervical lesions (CIN1). Further, we demonstrate HPV16 infection/differentiation-induced up-regulation of a specific subset of SR proteins and present evidence that HPV16 E2 controls expression of SRp20, SC35 and SRp75. Using a series of cell lines that model cervical tumour progression, we show that SF2/ASF, SRp20 and SC35 are specifically up-regulated in a model of cervical tumour progression. These SR proteins are also over-expressed in high-grade cervical lesions, indicating that they may all have oncogenic functions. SR proteins could be useful biomarkers for HPV-associated disease.

IGF1 mRNA isoform expression in the cervix of HPV-positive women with pre-cancerous and cancer lesions

“…it was previously described that hpV proteins also regulate gene expression at the transcriptional level and affect splicing by the up-regulation of splicing factors. in fact, the hpV E2 protein acts as a transcription factor, not only in terms of viral gene regulation, but also by altering the expression of multiple cellular genes, including splicing factors Sr (arginine/serine-rich splicing factor protein family), splicing factor 2/alternative splicing factor (SF/aSF) and heterogeneous nuclear ribonucleoprotein a1 (hnRNPA1) (29,30).…”

Human Papillomavirus 16 Oncoprotein Expression Is Controlled by the Cellular Splicing Factor SRSF2 (SC35)

“…Previously, we demonstrated that the three smallest SR proteins, SRSF1, SRSF2, and SRSF3, are overexpressed during cervical tumor progression (24), suggesting that they may possess cervical tumor-promoting activities. Figure 2 shows that these three proteins are overexpressed in W12t and W12ti tumor cells (lanes 3 and 4), compared to a much lower expression level in the W12E and W12G nontumor cells (lanes 1 and 2).…”

“…Apart from RNA processing-related functions, SR proteins have also been shown to be involved in chromatin remodelling, transcriptional regulation, genome stability maintenance, nucleolar stress, cell cycle progression, apoptosis control, and protein sumoylation (15)(16)(17)(18)(19)(20). Unsurprisingly, due to their diverse functions, many SR proteins are overexpressed in a range of tumors (21)(22)(23)(24)(25). Importantly, SRSF1 (ASF/SF2), SRSF3 (SRp20), and SRSF9 (SRp30c) have been shown to possess oncogenic properties (22)(23)(24)(25)(26)(27)(28)(29)(30)(31).…”

“…Unsurprisingly, due to their diverse functions, many SR proteins are overexpressed in a range of tumors (21)(22)(23)(24)(25). Importantly, SRSF1 (ASF/SF2), SRSF3 (SRp20), and SRSF9 (SRp30c) have been shown to possess oncogenic properties (22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Increased SRSF levels can result in the production of alternatively spliced RNA isoforms encoding key antiapoptotic, cell proliferation, and epithelial-mesenchymal transition (EMT)-inducing proteins (18).…”

“…Increased expression levels of SRSFs 1, 2, and 3 in cervical tumor cells and samples from patients with HPV-positive cervical lesions (24) prompted an investigation of a possible oncogenic role of SR proteins in cervical cancer. Here, we examine the effect of SRSF depletion on E6E7 mRNA production in cervical tumor cells.…”