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Functional domains of murine cytomegalovirus nuclear egress protein M53/p38

Mark Lötzerich1, Zsolt Ruzsics, Ulrich H Koszinowski

  • 1Max von Pettenkofer Institut, Pettenkoferstrasse 9a, 80336 Munich, Germany.

Journal of Virology
|December 15, 2005
PubMed

Insights

Mouse cytomegalovirus proteins M53/p38 and M50/p35 form a nuclear egress complex (NEC). Researchers mapped M53/p38

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • Herpes simplex virus 1 proteins UL31 and UL34 form a complex essential for nucleocapsid envelopment and nuclear egress.
  • In mouse cytomegalovirus (a betaherpesvirus), homologous proteins M53/p38 and M50/p35 constitute the nuclear egress complex (NEC).
  • Understanding the interaction and binding sites of these NEC components is crucial for deciphering herpesvirus replication mechanisms.

Purpose of the Study:

  • To map the binding site of M50/p35 on its interaction partner, M53/p38, within the mouse cytomegalovirus nuclear egress complex (NEC).
  • To investigate the functional importance of specific domains and amino acids within M53/p38 for NEC formation and viral replication.

Main Methods:

  • Comprehensive random mutagenesis of the M53/p38 gene.
  • Complementation assays to assess the viability of mutants lacking functional M53/p38.
  • Analysis of protein colocalization and coprecipitation to study M53/p38 and M50/p35 interactions.
  • Identification of nuclear localization signals and specific amino acid residues critical for function.

Main Results:

  • The N-terminal one-third of M53/p38 contains a crucial nuclear localization signal.
  • The binding site for M50/p35 was localized to amino acids 112 to 137 of M53/p38.
  • While single amino acid substitutions within this region did not abolish NEC formation, specific residues (K128, Y129, L130) were identified as important for reducing viral attenuation.
  • Mutations affecting the C-terminus of M53/p38 resulted in lethal phenotypes, highlighting its functional significance.

Conclusions:

  • The study successfully mapped the M50/p35 binding site on M53/p38, revealing key residues involved in nuclear egress complex function.
  • The N-terminus of M53/p38 is essential for nuclear localization, while specific internal and C-terminal regions are critical for M50/p35 interaction and overall NEC functionality.
  • These findings provide a detailed molecular understanding of the mouse cytomegalovirus nuclear egress complex and its role in the viral life cycle.

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