HPV-16 E2 contributes to induction of HPV-16 late gene expression by inhibiting early polyadenylation

Abstract

We provide evidence that the human papillomavirus (HPV) E2 protein regulates HPV late gene expression. High levels of E2 caused a read-through at the early polyadenylation signal pAE into the late region of the HPV genome, thereby inducing expression of L1 and L2 mRNAs. This is a conserved property of E2 of both mucosal and cutaneous HPV types. Induction could be reversed by high levels of HPV-16 E1 protein, or by the polyadenylation factor CPSF30. HPV-16 E2 inhibited polyadenylation in vitro by preventing the assembly of the CPSF complex. Both the N-terminal and hinge domains of E2 were required for induction of HPV late gene expression in transfected cells as well as for inhibition of polyadenylation in vitro. Finally, overexpression of HPV-16 E2 induced late gene expression from a full-length genomic clone of HPV-16. We speculate that the accumulation of high levels of E2 during the viral life cycle, not only turns off the expression of the pro-mitotic viral E6 and E7 genes, but also induces the expression of the late HPV genes L1 and L2.

Human Papillomavirus E2 Regulates SRSF3 (SRp20) To Promote Capsid Protein Expression in Infected Differentiated Keratinocytes

“…E2 appears to be required for induction of HPV late mRNA expression by inhibiting the viral early polyadenylation signal through interaction with CPSF30 (11). Although in our study an HPV31 E2 transactivation domain point mutant was all that was required to reduce virus capsid protein expression, in the study by Johannson et al both the E2 transactivation domain and the hinge region were required for control of the L1 and L2 mRNA levels (11). This suggests that there at least two E2-regulated mechanisms for controlling the viral late gene expression, and these are not mutually exclusive.…”

“…Expression of virus capsid proteins is known to be controlled not only at the level of transcription initiation but also at various posttranscriptional levels, including polyadenylation, alternative splicing, nuclear export, mRNA stability, and translation (2,(8)(9)(10)(11)(12). Notably, at least 13 mRNAs are produced late in the virus life cycle that contain open reading frames encoding the capsid proteins (10).…”

NP1 Protein of the Bocaparvovirus Minute Virus of Canines Controls Access to the Viral Capsid Genes via Its Role in RNA Processing

“…Recently, the HPV-16 E2 protein was reported to regulate the usage of the proximal polyadenylation cisacting elements in the middle of its genome by modulating the recruitment of the polyadenylation machinery to this site (44,45). In addition, viral proteins such as herpes simplex virus 1 (HSV-1) ICP27 (46,47), the Kaposi sarcoma-associated herpesvirus (KSHV) ORF57 protein (48)(49)(50), and the human cytomegalovirus protein UL69 (51,52) have been shown to modulate the processing of HSV, KSHV, and HCMV transcripts, respectively.…”

Human Papillomavirus Type 1 E1^E4 Protein Is a Potent Inhibitor of the Serine-Arginine (SR) Protein Kinase SRPK1 and Inhibits Phosphorylation of Host SR Proteins and of the Viral Transcription and Replication Regulator E2

“…Interestingly, the HPV16 E2 protein, whose hinge region does not contain RS dipeptide motifs, also associates with multiple SR proteins (61). The interaction with cellular splicing factors may contribute to E2-mediated posttranscriptional regulation of cellular and/or viral gene expression during the virus life cycle (60)(61)(62). However, in the case of HPV1 E2, we have been unable to identify interactions between SR proteins (HA-tagged forms of SRSF1 to -4 and SRSF7) and unphosphorylated or SRPK1 phosphorylated forms of the E2 protein (M.…”