Evolution-Guided Structural and Functional Analyses of the HERC Family Reveal an Ancient Marine Origin and Determinants of Antiviral Activity.

In humans, homologous to the E6-AP carboxyl terminus (HECT) and regulator of chromosome condensation 1 (RCC1)-like domain-containing protein 5 (HERC5) is an interferon-induced protein that inhibits replication of evolutionarily diverse viruses, including human immunodeficiency virus type 1 (HIV-1). To better understand the origin, evolution, and function of HERC5, we performed phylogenetic, structural, and functional analyses of the entire human small-HERC family, which includes HERC3, HERC4, HERC5, and HERC6. We demonstrated that the HERC family emerged >595 million years ago and has undergone gene duplication and gene loss events throughout its evolution. The structural topology of the RCC1-like domain and HECT domains from all HERC paralogs is highly conserved among evolutionarily diverse vertebrates despite low sequence homology. Functional analyses showed that the human small HERCs exhibit different degrees of antiviral activity toward HIV-1 and that HERC5 provides the strongest inhibition. Notably, coelacanth HERC5 inhibited simian immunodeficiency virus (SIV), but not HIV-1, particle production, suggesting that the antiviral activity of HERC5 emerged over 413 million years ago and exhibits species- and virus-specific restriction. In addition, we showed that both HERC5 and HERC6 are evolving under strong positive selection, particularly blade 1 of the RCC1-like domain, which we showed is a key determinant of antiviral activity. These studies provide insight into the origin, evolution, and biological importance of the human restriction factor HERC5 and the other HERC family members.IMPORTANCE Intrinsic immunity plays an important role as the first line of defense against viruses. Studying the origins, evolution, and functions of proteins responsible for effecting this defense will provide key information about virus-host relationships that can be exploited for future drug development. We showed that HERC5 is one such antiviral protein that belongs to an evolutionarily conserved family of HERCs with an ancient marine origin. Not all vertebrates possess all HERC members, suggesting that different HERCs emerged at different times during evolution to provide the host with a survival advantage. Consistent with this, two of the more recently emerged HERC members, HERC5 and HERC6, displayed strong signatures of having been involved in an ancient evolutionary battle with viruses. Our findings provide new insights into the evolutionary origin and function of the HERC family in vertebrate evolution, identifying HERC5 and possibly HERC6 as important effectors of intrinsic immunity in vertebrates.

Interferon-Induced HERC5 Inhibits Ebola Virus Particle Production and Is Antagonized by Ebola Glycoprotein.

Survival following Ebola virus (EBOV) infection correlates with the ability to mount an early and robust interferon (IFN) response. The host IFN-induced proteins that contribute to controlling EBOV replication are not fully known. Among the top genes with the strongest early increases in expression after infection in vivo is IFN-induced HERC5. Using a transcription- and replication-competent VLP system, we showed that HERC5 inhibits EBOV virus-like particle (VLP) replication by depleting EBOV mRNAs. The HERC5 RCC1-like domain was necessary and sufficient for this inhibition and did not require zinc finger antiviral protein (ZAP). Moreover, we showed that EBOV (Zaire) glycoprotein (GP) but not Marburg virus GP antagonized HERC5 early during infection. Our data identify a novel 'protagonist-antagonistic' relationship between HERC5 and GP in the early stages of EBOV infection that could be exploited for the development of novel antiviral therapeutics.

Modern treatment outcomes for early T-stage oropharyngeal cancer treated with intensity-modulated radiation therapy at a tertiary care institution.

BACKGROUND: Transoral surgery (TOS), particularly transoral robotic surgery (TORS) has become the preferred modality in the United States for the treatment of early stage oropharyngeal cancer, largely due to assumptions of fewer toxicities and improved quality of life compared to primary radiotherapy (RT). However, these assumptions are based on retrospective analysis, a subset of which utilize primary RT groups not limited to T1-2 stage tumors for which transoral robotic surgery is FDA approved. Thus, there is potential for underestimating survival and overestimating toxicity, including treatment related mortality, in primary RT. METHODS: Consecutive cases of early T-stage (T1-T2) oropharyngeal cancer presenting to the London Health Sciences Centre between 2014 and 2018 treated with RT or chemoradiation (CRT) were reviewed. Patient demographics, treatment details, survival outcomes and toxicity were collected. Toxicities were retrospectively graded using the Common Terminology Criteria for Adverse Events criteria. RESULTS: A total of 198 patients were identified, of which 82% were male and 73% were HPV-positive. Sixty-eight percent of patients experienced a grade 2 toxicity, 48% a grade 3 and 4% a grade 4. The most frequent toxicities were dysphagia, neutropenia and ototoxicity. The rates of gastrostomy tube dependence at 1 and 2 years were 2.5% and 1% respectively. There were no grade 5 (fatal) toxicities. HPV-positive patients experienced improved 5-year overall survival (86% vs 64%, p = 0.0026). CONCLUSIONS: Primary RT or CRT provides outstanding survival for early T-stage disease, with low rates of severe toxicity and feeding tube dependence. This study provides a reference for comparison for patients treated with primary transoral surgery.