Restoration of senescence in breast and ovarian cancer cells following the transfer of the YAC carrying SEN6A gene located at 6q16.3.

We previously located a senescence gene locus (SEN6A), at chromosome 6q14-21 by a functional strategy using chromosome transfer into immortal ovarian tumor cells. To further elucidate the SEN6A locus, intact chromosome 6 or 6q was transferred into rat ovarian tumor cells and a panel of immortal revertant clones of senescent cells was generated. The panel of independent colonies as well as mixed populations of revertant cells was analyzed for the presence or absence of chromosome 6 specific markers. These investigations led to the identification of a fine deletion of approximately 1cM at chromosomal interval 6q16.3. A contiguous stretch containing five yeast artificial chromosome (YAC) clones was constructed across the deleted region. The non-chimeric YAC clones were retrofitted and transferred into mouse A9 cells by spheroplast fusion to generate YAC/A9 hybrids. YAC DNA present in YAC/A9 hybrids was subsequently transferred by microcell fusion into immortal tumor cells, and the hybrid cells were characterized for their senescence phenotype. Using this functional strategy, the transfer of YAC clone 966b10 was shown to restore senescence in both rat and human ovarian and breast tumor cells. Our results demonstrate that the SEN6A gene is carried on a 1 Mb YAC, 966b10, which maps at 6q16.3.