Kinase Activity of Fibroblast Growth Factor Receptor 3 Regulates Activity of the Papillomavirus E2 Protein

Abstract

The papillomavirus (PV) E2 protein is a DNA binding, protein interaction platform that recruits viral and host factors necessary for transcription and replication. We recently discovered phosphorylation of a tyrosine (Y102) in bovine PV (BPV) E2. To identify the responsible factor, we tested several candidate tyrosine kinases that are highly expressed in keratinocytes for binding to BPV-1 E2. Fibroblast growth factor receptor 3 (FGFR3) coimmunoprecipitated with the BPV-1 E2 protein, as did human papillomavirus 31 (HPV-31) E2, which also colocalized with FGFR3 within the nucleus. A constitutively active mutant form of FGFR3 decreased BPV-1 and HPV-31 transient replication although this result also occurred in a BPV-1 E2 mutant lacking a previously identified phosphorylation site of interest (Y102). Furthermore, FGFR3 depletion in cell lines that maintain HPV-31 episomes increased viral copy number. These results suggest that FGFR3 kinase activity may regulate the PV reproductive program through phosphorylation of the E2 protein although this is unlikely to occur through the Y102 residue of HPV E2. The papillomavirus (PV) is a double-stranded DNA tumor virus infecting cervix, mouth, and throat tissues. The viral protein E2 is responsible for the replication of the virus. Understanding the mechanisms of the replicative life cycle of the virus may bring to light direct targets and treatments against viral infection. We recently found that the fibroblast growth factor receptor 3 (FGFR3) interacts with and mediates PV E2 function through phosphorylation of the E2 protein. Our study suggests that the function of the E2 protein may be regulated through a direct FGFR3 target during the maintenance stage of the PV life cycle.

Phosphorylation of a Conserved Tyrosine in the Papillomavirus E2 Protein Regulates Brd4 Binding and Viral Replication

“…1C) (20). We previously reported that coexpression of the constitutively kinase-active FGFR3 K650E suppresses HPV-31 E1-and E2-mediated transient replication, so the Y138E result was consistent with this phenotype (12). These observations suggested that Y138 is the target of FGFR3.…”

“…This led to the identification of fibroblast growth receptor 3 (FGFR3) as a candidate E2 interaction partner. However, our results indicated that BPV-1 Y102 was unlikely to be the target of the FGFR3 kinase, since Y102F-mediated transient replication was still susceptible to FGFR3 inactivation (12). These findings inferred that another Y residue(s) in PV E2 was phosphorylated by FGFR3.…”

“…FGFR3 phosphorylates HPV-31 E2 at Y138. Previous experiments implied that FGFR3 phosphorylation of the PV E2 protein suppressed viral DNA replication (12). This initially led us to test the conserved tyrosine residues within the TAD of E2 as the substrates for phosphorylation in this assay.…”

“…We previously reported that phosphorylation of Y102 impaired viral replication and transcription in bovine papillomavirus (BBPV) E2 (7). Our subsequent publication revealed that FGFR3 induced phosphorylation of E2 and inhibited viral DNA replication; however, this outcome also occurred with Y102F, inferring that this tyrosine is not the target of this kinase (12). We therefore sought to identify the tyrosine residue(s) that is responsible for the inhibitory effects of FGFR3.…”

Activity of CK2α protein kinase is required for efficient replication of some HPV types

“…Protein kinases that have been shown or suspected to be involved in the regulation of E1 and/or E2 activities and cellular localization include protein kinases A and C, MAP kinases, casein kinases 1 and 2, cyclin dependent kinase (cdk) and FGF receptor 3 [9][10][11][12][13][14][15][16]. Casein kinase 2 (CK2) is an ubiquitously expressed dual specificity protein kinase involved in almost all aspects of cellular life.…”