Using an sgRNA (ACAAAGTTGTCTTCTTCTAC), a donor oligonucleotide (AACTACTTAAATTACTGTTTTAAGTATACTAAATGTTTTTTATATTTTTCAGAAATTTTGGCGGAAGCATGCAGAAGAAGACAACTTTGTAAAGAATCTACTGCCTCTGAAGAACTAAGTAAGTATATT) and CRISPR/Cas9 technology, codons 647-649 were changed from LeuThrPro to AlaGluAla (p.Leu647_Pro649delinsAlaGluAla). This abolishes the telomeric repeat binding factor 1 (Terf1)-binding domain. (J:286164)