A cryptopromoter is activated in the proliferating cell nuclear antigen gene of growth arrested cells

We have examined the regulation of the proliferating cell nuclear antigen gene (PCNA) in a hamster fibroblast cell line (tk‐ts 13) which is temperature sensitive for growth. These tk‐ts 13 cells, at the restrictive temperature, are growth arrested in the G 1 phase of the cell cycle. The cells were stably transfected with a full length human PCNA gene, and the resulting cell lines (K525 cells) were analyzed. We find that, in growth arrested K525 cells, a cryptopromoter is activated in the transfected human PCNA gene. The cryptopromoter resides in intron 4 which is necessary for proper regulation of the PCNA gene. Removal of this intron leads to increased expression of PCNA in cells which have entered the G o state. An Alu sequence residing in intron 4 is implicated as the promoter element which is active during growth arrest. © 1992 Wiley‐Liss, Inc.