DNA-Packing Portal and Capsid-Associated Tegument Complexes in the Tumor Herpesvirus KSHV

• Published in: Cell Vol. 178; no. 6; pp. 1329 - 1343.e12
• Main Authors: Gong, Danyang, Dai, Xinghong, Jih, Jonathan, Liu, Yun-Tao, Bi, Guo-Qiang, Sun, Ren, Zhou, Z. Hong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.09.2019
• Subjects: capsid; Capsid - metabolism; Capsid Proteins - chemistry; cryo-EM; Cryoelectron Microscopy - methods; DNA Packaging; DNA, Viral - metabolism; gammaherpesvirus; genome; Genome, Viral; herpesvirus; Herpesvirus 8, Human - chemistry; Herpesvirus 8, Human - physiology; Humans; Kaposi's sarcoma-associated herpesvirus; microscopy; Models, Molecular; portal; Sarcoma, Kaposi - virology; tegument; virology; Virus Assembly; genome; gammaherpesvirus; Kaposi's sarcoma-associated herpesvirus; virology; herpesvirus; capsid; tegument; microscopy; portal; cryo-EM
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2019.07.035

Assembly of Kaposi’s sarcoma-associated herpesvirus (KSHV) begins at a bacteriophage-like portal complex that nucleates formation of an icosahedral capsid with capsid-associated tegument complexes (CATCs) and facilitates translocation of an ∼150-kb dsDNA genome, followed by acquisition of a pleomorphic tegument and envelope. Because of deviation from icosahedral symmetry, KSHV portal and tegument structures have largely been obscured in previous studies. Using symmetry-relaxed cryo-EM, we determined the in situ structure of the KSHV portal and its interactions with surrounding capsid proteins, CATCs, and the terminal end of KSHV’s dsDNA genome. Our atomic models of the portal and capsid/CATC, together with visualization of CATCs’ variable occupancy and alternate orientation of CATC-interacting vertex triplexes, suggest a mechanism whereby the portal orchestrates procapsid formation and asymmetric long-range determination of CATC attachment during DNA packaging prior to pleomorphic tegumentation/envelopment. Structure-based mutageneses confirm that a triplex deep binding groove for CATCs is a hotspot that holds promise for antiviral development. [Display omitted] •Genome-packing portal and capsid-associated tegument complexes (CATCs) resolved•Partial and asymmetric CATC occupancy introduces structural variability•CATC binding introduces 120° counterclockwise rotation of triplex Ta on the capsid•Structure-based mutageneses reveal binding hotspot for antiviral development Resolution of KSHV’s asymmetric icosahedral structure is achieved via symmetry-relaxed cryo-EM using sequential localized classification. Interactions between the DNA-translocating portal protein, associated capsid and tegument proteins, and the viral genome reveal surprising variability in tegument protein occupancy and orientation plasticity.