Installation of an Indole on the BRCA1 Disordered Domain Using Triazine Chemistry

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Engineering

Background:

• Protein sidechain functionalization is crucial for attaching labels and tags.
• Chlorotriazines are common reagents for protein modification via nucleophilic aromatic substitution.
• BRCA1 is a key tumor suppressor protein involved in DNA repair.

Purpose of the Study:

• To develop a method for labeling the disordered domain of BRCA1 with an indole tag.
• To assess the impact of indole labeling on BRCA1 structure and function.
• To characterize the interaction of indole-labeled BRCA1 with its binding partner, PALB2.

Main Methods:

• Nucleophilic aromatic substitution reaction using a poorly soluble dichlorotriazine with an indole group.
• Proteolytic cleavage to remove SUMO-tag and purification using N-terminal poly(His) tag.
• Characterization using steady-state fluorescence, circular dichroism spectroscopy, and isothermal titration calorimetry.
• Mass spectrometry for confirming single modification.

Main Results:

• The indole tag was successfully appended to the BRCA1 construct.
• Indole labeling did not significantly alter the structure or function of BRCA1.
• The indole-labeled BRCA1 maintained its binding affinity for PALB2.
• Mass spectrometry confirmed single modification, but precise location was undetermined.

Conclusions:

• The developed indole labeling method is suitable for modifying BRCA1 without compromising its integrity.
• This technique allows for the study of BRCA1 structure-function relationships and interactions.
• Further optimization of mass spectrometry methods may be needed to pinpoint modification sites.