SENESCENCE OF IMMORTAL HUMAN FIBROBLASTS BY THE INTRODUCTION OF NORMAL HUMAN-CHROMOSOME-6

In these studies we show that introduction of a normal human chromosom e 6 or 6q can suppress the immortal phenotype of simian virus 40-trans formed human fibroblasts (SV/HF). Normal human fibroblasts have a limi ted life span in culture. Immortal clones of SV/HF displayed nonrandom rearrangements in chromosome 6. Single human chromosomes present in m ouse/human monochromosomal hybrids were introduced into SV/HF via micr ocell fusion and maintained by selection for a dominant selectable mar ker gpt, previously integrated into the human chromosome. Clones of SV /HF cells bearing chromosome 6 displayed Limited potential for cell di vision and morphological characteristics of senescent cells. The loss of chromosome 6 from the suppressed clones correlated with the reappea rance of immortal clones. Introduced chromosome 6 in the senescing cel ls was distinguished from those of parental cells by the analysis for DNA sequences specific for the donor chromosome. Our results further s how that suppression of immortal phenotype in SV/HF is specific to chr omosome 6. Introduction of individual human chromosomes 2, 8, or 19 di d not impart cellular senescence in SV/HF. In addition, introduction o f chromosome 6 into human glioblastoma cells did not lead to senescenc e. Based upon these results we propose that at least one of the genes (SEN6) for cellular senescence in human fibroblasts is present on the long arm of chromosome 6.