The complex regulatory role of cytomegalovirus nuclear egress protein pul50 in the production of infectious virus

Häge S, Büscher N, Pakulska V, Hahn F, Adrait A, Krauter S, Borst EM, Schlötzer-Schrehardt U, Couté Y, Plachter B, Marschall M (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Book Volume: 10

Article Number: 3119

Journal Issue: 11

DOI: 10.3390/cells10113119

Abstract

The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recruits several viral and cellular factors by direct and indirect con-tacts. Recently, we generated an ORF-UL50-deleted recombinant HCMV in pUL50-complementing cells and obtained first indications of putative additional functions of pUL50. In this study, we produced purified ∆UL50 particles under both complementing (∆UL50C) and non-complementing (∆UL50N) conditions and performed a phenotypical characterization. Findings were as follows: (i) ∆UL50N particle preparations exhibited a clear replicative defect in qPCR-based infection kinetics compared to ∆UL50C particles; (ii) immuno-EM analysis of ∆UL50C did not reveal major changes in nuclear distribution of pUL53 and lamin A/C; (iii) mass spectrometry-based quantitative proteomics showed a large concordance of protein contents in the NIEP fractions of ∆UL50C and ∆UL50N particles, but virion fraction was close to the detection limit for ∆UL50N; (iv) confocal imaging of viral marker proteins of immediate early (IE) and later phases of ∆UL50N infection indicated a very low number of cells showing an onset of viral lytic protein expression; and, finally (v) quantitative measurements of encapsidated genomes provided evidence for a substantial reduction in the DNA contents in ∆UL50N compared to ∆UL50C particles. In summary, the results point to a complex and important regulatory role of the HCMV nuclear egress protein pUL50 in the maturation of infectious virus.

Authors with CRIS profile

Involved external institutions

University of Grenoble Alpes (UGA) / Université de Grenoble France (FR) Universitätsmedizin der Johannes Gutenberg-Universität Mainz Germany (DE) Medizinische Hochschule Hannover (MHH) / Hannover Medical School Germany (DE)

How to cite

APA:

Häge, S., Büscher, N., Pakulska, V., Hahn, F., Adrait, A., Krauter, S.,... Marschall, M. (2021). The complex regulatory role of cytomegalovirus nuclear egress protein pul50 in the production of infectious virus. Cells, 10(11). https://doi.org/10.3390/cells10113119

MLA:

Häge, Sigrun, et al. "The complex regulatory role of cytomegalovirus nuclear egress protein pul50 in the production of infectious virus." Cells 10.11 (2021).

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