A novel, evolutionarily conserved protein phosphatase complex involved in cisplatin sensitivity

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The DNA damage response is critical for maintaining genomic stability.
• Protein phosphatase 4 (PP4) is involved in DNA repair pathways.
• Understanding the composition and function of PP4 complexes is essential.

Purpose of the Study:

• To characterize a novel protein phosphatase 4 (PP4)-containing complex (PP4cs).
• To investigate the role of PP4cs in the eukaryotic DNA damage response.
• To identify novel components of the PP4 complex and their function.

Main Methods:

• Tandem affinity purification tagging and mass spectrometry were used to identify PP4cs components.
• Gene deletion studies in Saccharomyces cerevisiae were performed to assess sensitivity to cisplatin.
• Complementation experiments using human PP4R3 in yeast and analysis of Drosophila melanogaster mutants were conducted.

Main Results:

• A novel PP4-containing complex (PP4cs) was identified, comprising PP4C, PP4R2, and a new subunit, PP4R3.
• Deletion of PP4cs orthologs in S. cerevisiae resulted in hypersensitivity to cisplatin.
• Human PP4R3 complemented the yeast psy2 deletion, and Drosophila PP4R3 mutants showed cisplatin hypersensitivity, indicating a conserved role.
• PP4R3 may target PP4cs to DNA damage repair machinery via interaction with Rad53 (CHK2).

Conclusions:

• PP4cs is an evolutionarily conserved complex vital for the DNA damage response.
• The novel subunit PP4R3 plays a critical role in conferring resistance to DNA-damaging agents like cisplatin.
• PP4cs, potentially through PP4R3 and its interaction with Rad53, is a key player in DNA repair pathways.