Curriculum Guidelines for Graduate and Undergraduate Virology Courses.

Curriculum guidelines for virology are needed to best guide student learning due to the continuous and ever-increasing volume of virology information, the need to ensure that undergraduate and graduate students have a foundational understanding of key virology concepts, and the importance in being able to communicate that understanding to both other virologists and nonvirologists. Such guidelines, developed by virology educators and the American Society for Virology Education and Career Development Committee, are described herein.

Components of the LINC and NPC complexes coordinately target and translocate a virus into the nucleus to promote infection.

Nuclear entry represents the final and decisive infection step for most DNA viruses, although how this is accomplished by some viruses is unclear. Polyomavirus SV40 transports from the cell surface through the endosome, the endoplasmic reticulum, and the cytosol from where it enters the nucleus to cause infection. Here we elucidate the nuclear entry mechanism of SV40. Our results show that cytosol-localized SV40 is targeted to the nuclear envelope by directly engaging Nesprin-2 of the linker of nucleoskeleton and cytoskeleton (LINC) nuclear membrane complex. Additionally, we identify the NUP188 subunit of the nuclear pore complex (NPC) as a new Nesprin-2-interacting partner. This physical proximity positions the NPC to capture SV40 upon release from Nesprin-2, enabling the channel to facilitate nuclear translocation of the virus. Strikingly, SV40 disassembles during nuclear entry, generating a viral genome-VP1-VP3 subcomplex that efficiently crosses the NPC to enter the nucleus. Our results reveal how two major nuclear membrane protein complexes are exploited to promote targeting and translocation of a virus into the nucleus.

Using virtual interviewing to create a more accessible hybrid academic job market.

Virtual interviewing has become ubiquitous with the academic job market. Here, we highlight the best practices for candidates and departments to consider when using virtual interviewing. We propose how virtual interviews can be leveraged and adapted for hybrid academic job searches combining virtual and in-person activities in a post-pandemic world.

mSphere of Influence: Viruses-Pathogens or Expert Cell Biologists?

Chelsey C. Spriggs works in the field of DNA viral entry with a specific interest in virus-host interactions. In this mSphere of Influence article, she reflects on how two papers, "The HCMV assembly compartment is a dynamic Golgi-derived MTOC that controls nuclear rotation and virus spread" (D. J. Procter, A. Banerjee, M. Nukui, K. Kruse, et al., Dev Cell 45:83-100.e7, 2018, https://doi.org/10.1016/j.devcel.2018.03.010) and "Cytoplasmic control of intranuclear polarity by human cytomegalovirus" (D. J. Procter, C. Furey, A. G. Garza-Gongora, S. T. Kosak, D. Walsh, Nature 587:109-114, 2020, https://doi.org/10.1038/s41586-020-2714-x), impacted her research by reinforcing the scientific value in using viruses to understand cell biology.

Golgi-associated BICD adaptors couple ER membrane penetration and disassembly of a viral cargo.

During entry, viruses must navigate through the host endomembrane system, penetrate cellular membranes, and undergo capsid disassembly to reach an intracellular destination that supports infection. How these events are coordinated is unclear. Here, we reveal an unexpected function of a cellular motor adaptor that coordinates virus membrane penetration and disassembly. Polyomavirus SV40 traffics to the endoplasmic reticulum (ER) and penetrates a virus-induced structure in the ER membrane called "focus" to reach the cytosol, where it disassembles before nuclear entry to promote infection. We now demonstrate that the ER focus is constructed proximal to the Golgi-associated BICD2 and BICDR1 dynein motor adaptors; this juxtaposition enables the adaptors to directly bind to and disassemble SV40 upon arrival to the cytosol. Our findings demonstrate that positioning of the virus membrane penetration site couples two decisive infection events, cytosol arrival and disassembly, and suggest cargo remodeling as a novel function of dynein adaptors.

How non-enveloped viruses hijack host machineries to cause infection.

Viruses must navigate the complex endomembranous network of the host cell to cause infection. In the case of a non-enveloped virus that lacks a surrounding lipid bilayer, endocytic uptake from the plasma membrane is not sufficient to cause infection. Instead, the virus must travel within organelle membranes to reach a specific cellular destination that supports exposure or arrival of the virus to the cytosol. This is achieved by viral penetration across a host endomembrane, ultimately enabling entry of the virus into the nucleus to initiate infection. In this review, we discuss the entry mechanisms of three distinct non-enveloped DNA viruses-adenovirus (AdV), human papillomavirus (HPV), and polyomavirus (PyV)-highlighting how each exploit different intracellular transport machineries and membrane penetration apparatus associated with the endosome, Golgi, and endoplasmic reticulum (ER) membrane systems to infect a host cell. These processes not only illuminate a highly-coordinated interplay between non-enveloped viruses and their host, but may provide new strategies to combat non-enveloped virus-induced diseases.

Expression of HPV-induced DNA Damage Repair Factors Correlates With CIN Progression.

Human papillomaviruses (HPVs) are DNA viruses with epithelial tropism. High-risk types of HPV are the causative agents of the majority of cervical cancers and are responsible for a number of other anogenital as well as oropharyngeal cancers. The life cycle of HPV is closely linked to the differentiation state of its host cell and is dependent on the activation of specific pathways of the DNA damage response. Several proteins from the ataxia telangiectasia mutated and the ataxia telangiectasia mutated and Rad3-related DNA repair pathways, which are essential for maintaining genomic stability in cells, are upregulated in HPV-positive cells and are required for viral replication. Our studies examine the expression of 5 such DNA repair factors-pCHK2, pCHK1, FANCD2, BRCA1, and H2AX-in cervical specimens from patients diagnosed with low-grade, intermediate-grade, or high-grade lesions. The percentage of cells expressing pCHK2, pCHK1, FANCD2, and BRCA1 is significantly higher in high-grade squamous intraepithelial lesions compared with that of either low-grade squamous intraepithelial lesions or normal tissue, particularly in differentiated cell layers. In addition, the distribution of this staining throughout the epithelium is altered with increasing lesion grade. This study characterizes the expression of pCHK2, pCHK1, FANCD2, H2AX and BRCA1 during cervical cancer progression and provides additional insight into the role of these DNA damage response proteins in viral transformation.

Dynein Engages and Disassembles Cytosol-Localized Simian Virus 40 To Promote Infection.

During entry, polyomavirus (PyV) is endocytosed and sorts to the endoplasmic reticulum (ER), where it penetrates the ER membrane to reach the cytosol. From the cytosol, the virus moves to the nucleus to cause infection. How PyV is transported from the cytosol into the nucleus, a crucial infection step, is unclear. We found that upon reaching the cytosol, the archetypal PyV simian virus 40 (SV40) recruits the cytoplasmic dynein motor, which disassembles the viral particle. This reaction enables the resulting disassembled virus to enter the nucleus to promote infection. Our findings reveal how a cytosolic motor can be hijacked to impart conformational changes to a viral particle, a process essential for successful infection.IMPORTANCE How a nonenveloped virus successfully traffics from the cell surface to the nucleus to cause infection remains enigmatic in many instances. In the case of the nonenveloped PyV, the viral particle is sorted from the plasma membrane to the ER and then the cytosol, from which it enters the nucleus to promote infection. The molecular mechanism by which PyV reaches the nucleus from the cytosol is not entirely clear. Here we demonstrate that the prototype PyV SV40 recruits dynein upon reaching the cytosol. Importantly, this cellular motor disassembles the viral particle during cytosol-to-nucleus transport to cause infection.

Human Papillomavirus and the DNA Damage Response: Exploiting Host Repair Pathways for Viral Replication.

High-risk human papillomaviruses (HPVs) are the causative agents of cervical and other genital cancers. In addition, HPV infections are associated with the development of many oropharyngeal cancers. HPVs activate and repress a number of host cellular pathways to promote their viral life cycles, including those of the DNA damage response. High-risk HPVs activate the ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related (ATR) DNA damage repair pathways, which are essential for viral replication (particularly differentiation-dependent genome amplification). These DNA repair pathways are critical in maintaining host genomic integrity and stability and are often dysregulated or mutated in human cancers. Understanding how these pathways contribute to HPV replication and transformation may lead to the identification of new therapeutic targets for the treatment of existing HPV infections.

FANCD2 Binds Human Papillomavirus Genomes and Associates with a Distinct Set of DNA Repair Proteins to Regulate Viral Replication.

The life cycle of human papillomavirus (HPV) is dependent on the differentiation state of its host cell. HPV genomes are maintained as low-copy episomes in basal epithelial cells and amplified to thousands of copies per cell in differentiated layers. Replication of high-risk HPVs requires the activation of the ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related (ATR) DNA repair pathways. The Fanconi anemia (FA) pathway is a part of the DNA damage response and mediates cross talk between the ATM and ATR pathways. Our studies show that HPV activates the FA pathway, leading to the accumulation of a key regulatory protein, FANCD2, in large nuclear foci. These HPV-dependent foci colocalize with a distinct population of DNA repair proteins, including ATM components γH2AX and BRCA1, but infrequently with p-SMC1, which is required for viral genome amplification in differentiated cells. Furthermore, FANCD2 is found at viral replication foci, where it is preferentially recruited to viral genomes compared to cellular chromosomes and is required for maintenance of HPV episomes in undifferentiated cells. These findings identify FANCD2 as an important regulator of HPV replication and provide insight into the role of the DNA damage response in the differentiation-dependent life cycle of HPV.IMPORTANCE High-risk human papillomaviruses (HPVs) are the etiological agents of cervical cancer and are linked to the development of many other anogenital and oropharyngeal cancers. Identification of host cellular pathways involved in regulating the viral life cycle may be helpful in identifying treatments for HPV lesions. Mutations in genes of the Fanconi anemia (FA) DNA repair pathway lead to genomic instability in patients and a predisposition to HPV-associated malignancies. Our studies demonstrate that FA pathway component FANCD2 is recruited to HPV DNA, associates with members of the ATM DNA repair pathway, and is essential for the maintenance of viral episomes in basal epithelial cells. Disruption of the FA pathway may result in increased integration events and a higher incidence of HPV-related cancer. Our study identifies new links between HPV and the FA pathway that may help to identify new therapeutic targets for the treatment of existing HPV infections and cancers.