Topoisomerase IIβ-binding protein 1 activates expression of E2F1 and p73 in HPV-positive cells for genome amplification upon epithelial differentiation

Oncogene. 2019 Apr;38(17):3274-3287. doi: 10.1038/s41388-018-0633-1. Epub 2019 Jan 10.

Abstract

High-risk human papillomaviruses (HPVs) constitutively activate ataxia telangiectasia mutated (ATM) and ataxia telangiectasia- and Rad3-related (ATR) DNA damage repair pathways for viral genome amplification. HPVs activate these pathways through the immune regulator STAT-5. For the ATR pathway, STAT-5 increases expression of the topoisomerase IIβ-binding protein 1 (TopBP1), a scaffold protein that binds ATR and recruits it to sites of DNA damage. TopBP1 also acts as a transcriptional regulator, and we investigated how this activity influenced the HPV life cycle. We determined that TopBP1 levels are increased in cervical intraepithelial neoplasias as well as cervical carcinomas, consistent with studies in HPV-positive cell lines. Suppression of TopBP1 by shRNAs impairs HPV genome amplification and activation of the ATR pathway but does not affect the total levels of ATR and CHK1. In contrast, knockdown reduces the expression of other DNA damage factors such as RAD51 and Mre11 but not BRCA2 or NBS1. Interestingly, TopBP1 positively regulates the expression of E2F1, a TopBP1-binding partner, and p73 in HPV-positive cells in contrast to its effects in other cell types. TopBP1 transcriptional activity is regulated by AKT, and treatment with AKT inhibitors suppresses expression of E2F1 and p73 without interfering with ATR signaling. Importantly, the levels of p73 are elevated in HPV-positive cells and its knockdown impairs HPV genome amplification. This demonstrates that p73, like p63 and p53, is an important regulator of the HPV life cycle that is controlled by the transcriptional activating properties of the multifunctional TopBP1 protein.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins / genetics
  • Carrier Proteins / genetics*
  • Cell Differentiation / genetics*
  • Cell Line
  • Checkpoint Kinase 1 / genetics
  • DNA Damage / genetics
  • DNA-Binding Proteins / genetics*
  • E2F1 Transcription Factor / genetics*
  • Epithelial Cells / pathology*
  • Female
  • Gene Amplification / genetics*
  • Gene Expression Regulation / genetics
  • Humans
  • MRE11 Homologue Protein / genetics
  • Mice
  • NIH 3T3 Cells
  • Nuclear Proteins / genetics*
  • Papillomaviridae / pathogenicity
  • Papillomavirus Infections / genetics*
  • Rad51 Recombinase / genetics
  • STAT5 Transcription Factor / genetics
  • Signal Transduction / genetics
  • Transcription, Genetic / genetics
  • Tumor Protein p73 / genetics*
  • Uterine Cervical Dysplasia / genetics
  • Uterine Cervical Dysplasia / virology
  • Uterine Cervical Neoplasms / genetics
  • Uterine Cervical Neoplasms / virology

Substances

  • Carrier Proteins
  • DNA-Binding Proteins
  • E2F1 Transcription Factor
  • E2F1 protein, human
  • Nuclear Proteins
  • STAT5 Transcription Factor
  • TOPBP1 protein, human
  • TP73 protein, human
  • Tumor Protein p73
  • Ataxia Telangiectasia Mutated Proteins
  • Checkpoint Kinase 1
  • Rad51 Recombinase
  • MRE11 Homologue Protein