Identification of Marek’s Disease Virus VP22 Tegument Protein Domains Essential for Virus Cell-to-Cell Spread, Nuclear Localization, Histone Association and Cell-Cycle Arrest

Abstract

VP22 is a major tegument protein of alphaherpesviruses encoded by the UL49 gene. Two properties of VP22 were discovered by studying Marek’s disease virus (MDV), the Mardivirus prototype; it has a major role in virus cell-to-cell spread and in cell cycle modulation. This 249 AA-long protein contains three regions including a conserved central domain. To decipher the functional VP22 domains and their relationships, we generated three series of recombinant MDV genomes harboring a modified UL49 gene and assessed their effect on virus spread. Mutated VP22 were also tested for their ability to arrest the cell cycle, subcellular location and histones copurification after overexpression in cells. We demonstrated that the N-terminus of VP22 associated with its central domain is essential for virus spread and cell cycle modulation. Strikingly, we demonstrated that AAs 174-190 of MDV VP22 containing the end of a putative extended alpha-3 helix are essential for both functions and that AAs 159–162 located in the putative beta-strand of the central domain are mandatory for cell cycle modulation. Despite being non-essential, the 59 C-terminal AAs play a role in virus spread efficiency. Interestingly, a positive correlation was observed between cell cycle modulation and VP22 histones association, but none with MDV spread.

Pervasive differential splicing in Marek’s Disease Virus can discriminate CVI-988 vaccine strain from RB-1B virulent strain in chicken embryonic fibroblasts

“…The intron I1 we identified could potentially represent a new protein-coding transcript which is transcribed from the UL49 locus of MDV strain CVI-988. It is reported that the VP22 protein of MDV is involved in cell cycle arrest, virus spread and histone association during MDV replication in vitro (32). Further studies will be required in order to investigate the involvement of the I1 transcript in the interaction between virus and host.…”

Alphaherpesvirus Major Tegument Protein VP22: Its Precise Function in the Viral Life Cycle

“…X-ray crystallography has revealed that VP22 of HSV-1 shares extensive structural similarity with ORF52 of Murid herpesvirus-68 (MHV-68) (subfamily Gammaherpesvirinae ) ( Song et al, 2005 ; Bortz et al, 2007 ). Comparisons of the sequences of VP22 in different viruses have indicated that the core domain length is 78–79 amino acids and is present in different positions of VP22 homologs ( Trapp-Fragnet et al, 2019 ).…”

“…However, amino acids 191–249 of VP22 are not essential for MDV transmission; rather, they facilitate efficient cell-to-cell spread. Amino acids 174–190 are essential for MDV VP22 functionality, and the IKIT motif (amino acids 159–162), located in the predicted β-strand, plays key roles in nuclear localization, histone association, and cell cycle arrest ( Trapp-Fragnet et al, 2019 ) ( Table 2 ).…”

“…MDV VP22 has the same function as BoHV-1 VP22 during interactions with histones ( Trapp-Fragnet et al, 2014 ). Interestingly, a positive correlation between cell cycle modulation and VP22 histone association, but no relationship with MDV cell-to-cell spread function, has been observed ( Trapp-Fragnet et al, 2019 ).…”

UL28 and UL33 homologs of Marek’s disease virus terminase complex involved in the regulation of cleavage and packaging of viral DNA are indispensable for replication in cultured cells

“…Meanwhile, MDV-encoded tegument proteins perform both regulatory and structural roles in the viral replication. For instance, one of the major tegument protein VP22, encoded by UL49, was indispensable for the propagation of MDV mainly relying on its N-terminus central domain, which might affect viral replication through modulating cell cycle metabolism [ 10 ]. The tegument proteins in cluster UL46–UL49 are conserved and play different roles in viral replication.…”