title: A leucine residue in the C terminus of human parainfluenza virus type 3 matrix protein is essential for efficient virus-like particle and virion release.
abstract: Paramyxovirus particles, like other enveloped virus particles, are formed by budding from membranes of infected cells, and matrix (M) proteins are critical for this process. To identify the M protein important for this process, we have characterized the budding of the human parainfluenza virus type 3 (HPIV3) M protein. Our results showed that expression of the HPIV3 M protein alone is sufficient to initiate the release of virus-like particles (VLPs). Electron microscopy analysis confirmed that VLPs are morphologically similar to HPIV3 virions. We identified a leucine (L302) residue within the C terminus of the HPIV3 M protein that is critical for M protein-mediated VLP production by regulating the ubiquitination of the M protein. When L302 was mutated into A302, ubiquitination of M protein was defective, the release of VLPs was abolished, and the membrane binding and budding abilities of M protein were greatly weakened, but the ML302A mutant retained oligomerization activity and had a dominant negative effect on M protein-mediated VLP production. Furthermore, treatment with a proteasome inhibitor also inhibited M protein-mediated VLP production and viral budding. Finally, recombinant HPIV3 containing the M(L302A) mutant could not be rescued. These results suggest that L302 acts as a critical regulating signal for the ubiquitination of the HPIV3 M protein and virion release.
  
  
  OBJECTIVE
  Human parainfluenza virus type 3 (HPIV3) is an enveloped virus with a nonsegmented negative-strand RNA genome. It can cause severe respiratory tract diseases, such as bronchiolitis, pneumonia, and croup in infants and young children. However, no valid antiviral therapy or vaccine is currently available. Thus, further elucidation of its assembly and budding will be helpful in the development of novel therapeutic approaches. Here, we show that a leucine residue (L302) located at the C terminus of the HPIV3 M protein is essential for efficient production of virus-like particles (VLPs). Furthermore, we found L302 regulated M protein-mediated VLP production via regulation of M protein ubiquitination. Recombinant HPIV3 containing the M(L302A) mutant is growth defective. These findings provide new insight into the critical role of M protein-mediated VLP production and virion release of a residue that does not belong to L domain and may advance our understanding of HPIV3 viral assembly and budding.
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Guangyuan
authors.initials: G
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Shengwei
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Binbin
authors.initials: B
authors.lastname: Ding
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Longyun
authors.initials: L
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Yanliang
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhong
authors.affiliation: State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China chenmz@whu.edu.cn.
authors.forename: Mingzhou
authors.initials: M
authors.lastname: Chen
mesh_terms: D002460:Cell Line; D004252:DNA Mutational Analysis; D006801:Humans; D007930:Leucine / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D010224:Parainfluenza Virus 3, Human / Q000502:physiology*; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000378:metabolism*; D022701:Virosomes / Q000378:metabolism; D057074:Virus Release
chemical_list: D050505:Mutant Proteins; D014763:Viral Matrix Proteins; D022701:Virosomes; D007930:Leucine