High-risk human papillomavirus-18 uses an mRNA sequence to synthesize oncoprotein E6 in tumors
Menée à partir d'échantillons de carcinomes du col utérin et de néoplasies intraépithéliales cervicales de grade 3 infectés par le papillomavirus humain, cette étude identifie une séquence d'ARN messager bicistronique utilisée par le papillomavirus humain de type 18 pour contrôler la synthèse de l'oncoprotéine E6
Cervical cancer is the fourth most common cancer in women for both incidence and mortality worldwide. The causal agent is a group of viruses termed high-risk human papillomavirus (HPV). Viral types 16 and 18 cause
∼
70% of this burden disease. HPV E6 is a potent oncoprotein that plays a central role in carcinogenesis, but its synthesis remains poorly understood at the level of mRNA translation. We discovered that in cervical tumors, mRNAs possessing 5′ UTRs of 0 to 5 nucleotides and harboring the motif ACCaugGCGCG(C/A)UUU control E6 mRNA translation. This process is highly dependent on eIF4E and eIF4AI, two translation factors linking translation and cancer. We suggest the use of drugs targeting these factors as antineoplasic compounds for HPV-caused cancers.Cervical cancer is the fourth most common cause of cancer in women worldwide in terms of both incidence and mortality. Persistent infection with high-risk types of human papillomavirus (HPV), namely 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68, constitute a necessary cause for the development of cervical cancer. Viral oncoproteins E6 and E7 play central roles in the carcinogenic process by virtue of their interactions with cell master proteins such as p53, retinoblastoma (Rb), mammalian target of rapamycin (mTOR), and c-MYC. For the synthesis of E6 and E7, HPVs use a bicistronic messenger RNA (mRNA) that has been studied in cultured cells. Here, we report that in cervical tumors, HPV-18, -39, and -45 transcribe E6/E7 mRNAs with extremely short 5′ untranslated regions (UTRs) or even lacking a 5′ UTR (i.e., zero to three nucleotides long) to express E6. We show that the translation of HPV-18 E6 cistron is regulated by the motif ACCaugGCGCG(C/A)UUU surrounding the AUG start codon, which we term Translation Initiation of Leaderless mRNAs (TILM). This motif is conserved in all HPV types of the phylogenetically coherent group forming genus alpha, species 7, which infect mucosal epithelia. We further show that the translation of HPV-18 E6 largely relies on the cap structure and eIF4E and eIF4AI, two key translation initiation factors linking translation and cancer but does not involve scanning. Our results support the notion that E6 forms the center of the positive oncogenic feedback loop node involving eIF4E, the mTOR cascade, and p53.All study data are included in the article and/or SI Appendix.