The goal of our studies is to understand the mechanisms that regulate viral late gene expression and genome amplification during the productive life cycle of oncogenic human papillomaviruses (HPVs). Papillomaviruses are small DNA viruses that induce a variety of proliferative epithelial lesions. Infection by papillomaviruses occurs into the basal cells of the epithelia where genomes are established as low copy episomes. The life cycle of papillomaviruses is tightly linked to epithelial differentiation with the induction of late gene expression, genome amplification and assembly of virions restricted to suprabasal cells. My laboratory first developed methods to grow human papillomaviruses in tissue culture and extended these techniques to synthesize HPVs from cloned DNA. These methods have allowed for a detailed genetic analysis of the productive life cycle of human papillomaviruses. In the recent grant period we have identified sequences within the URR and the E6/E7 coding sequences that regulate late gene expression in differentiated cells. Our studies have also identified E2F2, C/EBP2, C/EBP1 as prime candidates to be the major regulators of late gene expression. Additional work demonstrated that HPV proteins activate caspases upon differentiation and that this is necessary for efficient genome amplification. We further determined that caspases target the E1 proteins and that this facilitates amplification. In this grant, I propose to investigate how late gene expression and amplification are regulated by asking the following questions: 1) How is HPV late gene expression regulated in differentiating epithelia? How do E2F2, C/EBP2, C/EBP1 function in the activation of late expression? Do viral proteins play a role in activating late expression independent of their role in mediating amplification? 2) What mechanisms regulate differentiation-dependent amplification? How do the caspase cleaved forms of E1 and E2 contribute to genome amplification in differentiating cells?

Public Health Relevance

Cervical cancer is the second leading cause of death by cancer in women worldwide and the overall 5-year survival rate is approximately 50%. In 2006, the FDA approved a prophylactic Human Papillomavirus (HPV) vaccine but this vaccine will not protect women against all the HPV types that cause cervical cancer. In addition, it is ineffective in clearing existing lesions as it only blocks initial infection. This study examines how the productive life cycle of these viruses is regulated through changes in viral gene expression and replication. This is an area of high importance as it can identify new targets for anti-viral treatments.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Virology - B Study Section (VIRB)
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Read-Connole, Elizabeth Lee
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Northwestern University at Chicago
Schools of Medicine
United States
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Mehta, Kavi; Laimins, Laimonis (2018) Human Papillomaviruses Preferentially Recruit DNA Repair Factors to Viral Genomes for Rapid Repair and Amplification. MBio 9:
Hong, Shiyuan; Cheng, Shouqiang; Songock, William et al. (2017) Suppression of MicroRNA 424 Levels by Human Papillomaviruses Is Necessary for Differentiation-Dependent Genome Amplification. J Virol 91:
Spriggs, Chelsey C; Laimins, Laimonis A (2017) Human Papillomavirus and the DNA Damage Response: Exploiting Host Repair Pathways for Viral Replication. Viruses 9:
Hong, Shiyuan; Laimins, Laimonis A (2017) Manipulation of the innate immune response by human papillomaviruses. Virus Res 231:34-40
Spriggs, Chelsey C; Laimins, Laimonis A (2017) FANCD2 Binds Human Papillomavirus Genomes and Associates with a Distinct Set of DNA Repair Proteins to Regulate Viral Replication. MBio 8:
Gunasekharan, Vignesh Kumar; Li, Yan; Andrade, Jorge et al. (2016) Post-Transcriptional Regulation of KLF4 by High-Risk Human Papillomaviruses Is Necessary for the Differentiation-Dependent Viral Life Cycle. PLoS Pathog 12:e1005747
Langsfeld, Erika; Laimins, Laimonis A (2016) Human papillomaviruses: research priorities for the next decade. Trends Cancer 2:234-240
Mehta, Kavi; Gunasekharan, Vignesh; Satsuka, Ayano et al. (2015) Human papillomaviruses activate and recruit SMC1 cohesin proteins for the differentiation-dependent life cycle through association with CTCF insulators. PLoS Pathog 11:e1004763
Hong, Shiyuan; Cheng, Shouqiang; Iovane, Andre et al. (2015) STAT-5 Regulates Transcription of the Topoisomerase II?-Binding Protein 1 (TopBP1) Gene To Activate the ATR Pathway and Promote Human Papillomavirus Replication. MBio 6:e02006-15
Langsfeld, Erika S; Bodily, Jason M; Laimins, Laimonis A (2015) The Deacetylase Sirtuin 1 Regulates Human Papillomavirus Replication by Modulating Histone Acetylation and Recruitment of DNA Damage Factors NBS1 and Rad51 to Viral Genomes. PLoS Pathog 11:e1005181

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