Differential Complex Formation via Paralogs in the Human Sin3 Protein Interaction Network.

Area of Science:

• Molecular Biology
• Proteomics
• Genetics

Background:

• Histone deacetylase (HDAC) inhibitors are under clinical investigation, but their target complexity hinders understanding of their effects.
• Sin3 complexes, conserved regulators of transcription, exist as two human paralogs, SIN3A and SIN3B, leading to poorly understood functional heterogeneity.

Purpose of the Study:

• To profile the interaction networks of human SIN3A and SIN3B.
• To elucidate the composition and organization of Sin3 complexes.
• To identify domains mediating interactions within Sin3 protein complexes.

Main Methods:

• Affinity purification coupled with mass spectrometry (AP-MS) to map protein interaction networks.
• Chemical cross-linking mass spectrometry (CX-MS) to identify interaction domains.
• Proteomic analysis of SIN3B proteoforms.

Main Results:

• Sin3 paralog identity significantly influences the composition of associated protein complexes.
• CX-MS identified specific domains involved in interactions between Sin3 proteins and their partners.
• Characterization of rare SIN3B proteoforms revealed conserved and divergent features within human Sin3 proteins.

Conclusions:

• Human SIN3A and SIN3B proteins exhibit both shared and distinct properties.
• The findings highlight the heterogeneous nature of Sin3-organized complexes, impacting transcriptional regulation.
• This work provides a foundation for dissecting the functional roles of specific Sin3 complexes.