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Molecular behavior of human Mrt4 protein, MRTO4, in stress conditions is regulated by its C-terminal region

Barbara Michalec-Wawiorka1, Leszek Wawiorka1, Kamil Derylo1

  • 1Department of Molecular Biology, Maria Curie-Sklodowska University, Akademicka 19, 20-033 Lublin, Poland.

The International Journal of Biochemistry & Cell Biology
|October 24, 2015
PubMed

Insights

Human Mrt4 protein phosphorylation by CK2 kinase regulates its behavior during nucleolar stress. This finding reveals a new link between ribosome biogenesis and cellular metabolism under stress conditions.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Ribosome biogenesis is crucial for cell function.
  • Protein Mrt4 is a trans-acting factor in ribosome biogenesis.
  • Mrt4 shares similarities with ribosomal P proteins.

Purpose of the Study:

  • To investigate the phosphorylation of human Mrt4 (hMrt4).
  • To identify the kinase responsible for hMrt4 phosphorylation.
  • To understand the functional consequences of hMrt4 phosphorylation during cellular stress.

Main Methods:

  • In vivo and in vitro phosphorylation assays.
  • Site-directed mutagenesis to identify phosphorylation sites.
  • Subcellular localization studies.
  • Analysis of molecular behavior during Actinomycin D (ActD) induced stress.

Main Results:

  • hMrt4 undergoes in vivo phosphorylation.
  • CK2 kinase phosphorylates serines S229, S233, and S235 in the acidic C-terminus of hMrt4 in vitro.
  • Phosphorylation does not affect hMrt4 localization under normal conditions.
  • Phosphorylation alters hMrt4 behavior during ActD-induced nucleolar stress.

Conclusions:

  • CK2-mediated phosphorylation of hMrt4 is a regulatory mechanism.
  • This modification plays a role in the cellular stress response.
  • A novel regulatory pathway connecting ribosome biogenesis and cellular metabolism under stress is proposed.
Keywords:
Nucleolar stressProtein phosphorylationRibosomal stalkRibosome biogenesishMrt4/MRTO4 protein

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