BRCA2-RAD51-IN-3

CRISPR-Cas9 HDR knock-in uses a guide RNA to direct Cas9 to a genomic target adjacent to a PAM, where Cas9 creates a double-strand break; if a donor DNA template with homology to the cut region is present, cellular HDR can copy the donor sequence into the genome, producing a precise substitution, tag, reporter, or insertion rather than an indel. The readout is the fraction of alleles or cells carrying the intended donor-derived edit, measured by junction PCR, restriction-fragment analysis, Sanger sequencing, amplicon deep sequencing, flow cytometry for reporter knock-in, or clone genotyping; NHEJ indels and partial or non-HDR insertions are measured in parallel because they compete with or confound precise HDR outcomes.

The pull-down assay is an in vitro technique used to detect physical interactions between two or more proteins and an invaluable tool for confirming a predicted protein-protein interaction or identifying novel interacting partners. This method typically involves the use of affinity purification with various wash and elution steps.

Immunoprecipitation (IP) is an experimental method that uses the principle of antibody specific binding to purify and enrich target proteins.

Bimolecular fluorescence complementation detects protein-protein proximity in living or fixed cells by fusing two candidate interaction partners to nonfluorescent N- and C-terminal fragments of a fluorescent protein; when the partners interact or remain close enough, the fluorescent fragments complement, mature, and generate a fluorescent signal at the site of the protein complex. The BiFC readout is fluorescence intensity and subcellular localization of the reconstituted fluorophore, which reflects formation or stabilization of a protein complex rather than direct biochemical binding kinetics; BiFC is therefore useful for mapping where interactions occur in cancer cells, neurons, macrophages, organoid-derived cells, or drug-screening systems, but results should be validated by independent assays such as co-IP or Western blot. BiFC signal formation is delayed by fluorophore maturation and can stabilize otherwise transient complexes, so it is not a real-time reversible interaction assay

Co-immunoprecipitation technology can verify protein interaction based on the specific immune reaction between antibodies and antigens.

The yeast two-hybrid assay detects binary protein-protein interactions by separating a transcription factor into a DNA-binding domain fused to a "bait" protein and a transcriptional activation domain fused to a "prey" protein; if bait and prey interact in yeast, the transcription factor is reconstituted and activates reporter genes such as HIS3, ADE2, lacZ, MEL1, or other selectable/readable reporters. The readout is yeast growth on selective medium and/or reporter activity, which reflects proximity-dependent transcriptional activation in the yeast nucleus rather than direct biochemical binding in the original mammalian, tumor, neuronal, macrophage, or organoid context. Because yeast two-hybrid can generate false positives and false negatives, interaction claims should be validated using independent assays such as co-immunoprecipitation, Western blot, immunofluorescence colocalization, BiFC, pull-down, or mammalian two-hybrid assays.