BRCA1 affects protein phosphatase 6 signalling through its interaction with ANKRD28

Area of Science:

• Cell Biology
• Molecular Oncology
• Signal Transduction

Background:

• The tumor suppressor BRCA1 (breast and ovarian cancer-susceptibility gene 1) is known for its nuclear roles in DNA repair and transcription.
• BRCA1 also exhibits cytoplasmic functions, including pro-apoptotic activity.

Purpose of the Study:

• To identify novel BRCA1-interacting proteins.
• To investigate the functional consequences of the BRCA1-ANKRD28 interaction in cytoplasmic signaling pathways.

Main Methods:

• Yeast two-hybrid screening to identify interacting proteins.
• Reciprocal immunoprecipitation and co-immunoprecipitation to confirm protein interactions.
• Proximity ligation assay to determine subcellular localization of the interaction.
• Western blotting to assess protein stability (IκBε) under different conditions.

Main Results:

• ANKRD28 (ankyrin repeat domain 28) was identified as a novel BRCA1-interacting protein, with the interaction confirmed in the cytoplasm.
• ANKRD28 silencing destabilized IκBε (inhibitor of nuclear factor κBε) by activating protein phosphatase 6 (PP6) upon TNFα stimulation.
• BRCA1 overexpression stabilized IκBε, an effect dependent on its interaction with ANKRD28.

Conclusions:

• BRCA1 modulates PP6 signaling through its cytoplasmic interaction with ANKRD28.
• This novel cytoplasmic mechanism involving BRCA1 and ANKRD28 may contribute to BRCA1's tumor-suppressive functions.