Mapping the Subtype-Specific PARP1 ADP-ribosylated Proteome in Breast Cancer Cells

Area of Science:

• Molecular Biology
• Cancer Research
• Biochemistry

Background:

• Breast cancer exhibits molecular heterogeneity, influencing gene expression, chromatin structure, and treatment outcomes.
• Poly (ADP-ribose) polymerase 1 (PARP1) is known for DNA repair but also regulates gene expression.

Purpose of the Study:

• To investigate the role of PARP1 in gene expression regulation across different breast cancer subtypes.
• To map PARP1-mediated ADP-ribosylation substrates and identify subtype-specific modifications.

Main Methods:

• Utilized an NAD analog-sensitive PARP1 (asPARP1) chemical genetics approach.
• Employed mass spectrometry to identify ADP-ribosylated proteins across six human breast cancer cell lines (luminal and basal/triple-negative).

Main Results:

• Identified thousands of PARP1 substrates and hundreds of ADP-ribosylation sites, showing shared and subtype-specific patterns.
• Luminal-specific substrates included chromatin and transcriptional regulators; basal-specific substrates were linked to translation and RNA processing.
• Transcription factors, like TFAP2A, were key substrates, with PARP1 inhibition affecting their promoter occupancy in a subtype-specific manner.

Conclusions:

• PARP1 plays a significant role in subtype-specific gene regulation in breast cancer beyond DNA repair.
• Findings provide a resource for understanding PARP1-mediated ADP-ribosylation and its implications for breast cancer treatment sensitivity.