Nanog, in Cooperation with AP1, Increases the Expression of E6/E7 Oncogenes from HPV Types 16/18.

Yakelin Díaz-Tejeda,Patricio Gariglio-Vidal,Helga López-Carbajal,Rocío Méndez-Martínez,Alfredo Amador-Molina,Miriam C Guido-Jiménez,Marcela Lizano,Alejandro García-Carrancá

doi:10.3390/v13081482

Abstract

Persistent infections with some types of human papillomavirus (HPV) constitute the major etiological factor for cervical cancer development. Nanog, a stem cell transcription factor has been shown to increase during cancer progression. We wanted to determine whether Nanog could modulate transcription of E6 and E7 oncogenes. We used luciferase reporters under the regulation of the long control region (LCR) of HPV types 16 and 18 (HPV16/18) and performed RT-qPCR. We found that Nanog increases activity of both viral regulatory regions and elevates endogenous E6/E7 mRNA levels in cervical cancer-derived cells. We demonstrated by in vitro mutagenesis that changes at Nanog-binding sites found in the HPV18 LCR significantly inhibit transcriptional activation. Chromatin immunoprecipitation (ChIP) assays showed that Nanog binds in vivo to the HPV18 LCR, and its overexpression increases its binding as well as that of c-Jun. Surprisingly, we observed that mutation of AP1-binding sites also affect Nanog’s ability to activate transcription, suggesting cooperation between the two factors. We searched for putative Nanog-binding sites in the LCR of several HPVs and surprisingly found them only in those types associated with cancer development. Our study shows, for the first time, a role for Nanog in the regulation of E6/E7 transcription of HPV16/18.

Highlights

Nanog has been shown to be expressed in malignant tumors of the uterine cervix, and high expression associated with poor tumor prognosis [46,47]
We studied the effect of Nanog in the transcriptional regulation of
We observed that Nanog significantly increases transcriptional activities from the both long control region (LCR)

Summary

Introduction

16, 18, 31, 33, 35, 39, 45, 51, 52, 56, and 59 are known as high-risk (hr-HPV) types, most prominent members found in uterine cervix tumors are 16 and 18 [3]. HPV genomes are divided into three regions: a regulatory one encompassing the origin of replication and binding sequences for a plethora of transcription factors, called long control region (LCR), an early region containing non-structural genes (E1, E2, E4, E5, E6, and E7), and a late region containing L1 and L2 structural genes [4]. The LCR comprises roughly 800–900 bp and contains the early promoter driving expression of E6 and E7 oncogenes and a transcriptional enhancer with multiple transcription factor-binding sites (TBSs), including AP1, NF1, YY1, Sox, and Oct1 [5,6,7]

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