Figure 1. Genetically engineered p53-inducible cell line strategy for discovery of asymmetric self-renewal associated (ASRA) genes.

All cell lines are maintained in ZnCl₂-supplemented medium. Vector control, p53-Null cells exhibit symmetric self-renewal (SYM) under this condition. The SYM state is characterized by continuous cell divisions that produce two equivalent cycling cells (open circles). P53-inducible cells exhibit asymmetric self-renewal (ASYM) in response to p53 expression induced by ZnCl₂-supplementation. The ASYM state is characterized by continuous cell divisions that produce one cycling cell and one G1/S-arrested cell (closed circle; curved arrow indicates continuous asymmetric divisions by cycling stem-like cells). c-IMPDH II-expressing cells induce p53 as well, but maintain symmetric self-renewal (p53SYM). “ASRA-up” genes are defined as those that were undetectable or produced at low levels in both SYM and p53SYM states, but showed high levels of expression in the ASYM state. Genes with the reciprocal expression pattern are called “ASRA-down” genes.