SHLD2 and breast cancer: The C‐terminal of SHLD2 binds to ssDNA ends, preventing the resection of DNA ends by competing with EXO1 and DNA2.[10, 11] SHLD2 is essential for promoting NHEJ and antibody class switch recombination (CSR).[12] High expression of SHLD2 is associated with poor prognosis in breast cancer patients.[5, 13] However, little is known about the regulatory mechanisms governing SHLD2 activity.