In the Research Article “Efficient formation of single-copy human artificial chromosomes” by C.W. Gambogi et al. (21 March 2024, 10.1126/science.adj3566), the yeast strain harboring YAC-Mm-4q21LacO was found to be compromised. The origin of the problem with the yeast strain is not clear but may have involved either contamination with another strain from an earlier and separate artificial chromosome project at the J. Craig Venter Institute or initial introduction into a strain already harboring a YAC from that project. The identity of the YAC that formed functional human artificial chromosomes upon introduction into human cells was confirmed to be the reported YAC-Mm-4q21LacO. Therefore, the main conclusions of the paper are not affected by any issues that may have compromised the yeast strain at the time of the experimentation reported in the paper. YAC-Mm-4q21LacO was remade, starting from its component parts (prokaryotic stuffer DNA, mammalian expression cassettes encoding fluorescent protein and antibiotic selection genes, an array of LacO sites, and a 180-kb region human chromosome 4), and assembled in the host yeast strain, VL6-48N. The resulting strain harboring the remade YAC-Mm-4q21LacO was then sequenced and tested. The remade YAC-Mm-4q21LacO readily forms functional HACs in the two originally tested human cell lines (HT1080 and U2OS) and in a manner stimulated by the initial, transient expression of LacI-HJURP. The findings have been published (1). All of this is directly in line with what was reported in the paper. The remade YAC-containing strain is available from the corresponding author upon reasonable request.
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