Deregulated c-Fos/AP-1 accelerates cell cycle progression of B lymphocytes stimulated with lipopolysaccharide.

We implicated deregulated c-Fos/AP-1 in proliferative response of B lymphocytes stimulated with lipopolysaccharide (LPS) using splenic B cells from c-fos transgenic (Mx-c-fos) mice. Levels of DNA synthesis of the Mx-c-fos B cells were augmented in proportion to the amount of AP-1. Since the number of LPS-responding splenic B cells from Mx-c-fos mice was similar to that from control mice duplication time of the Mx-c-fos B cells (0.9 days) was much shorter than that of the control B cells (2.1 days), this augmentation is explained by the acceleration of cell cycle progression by deregulated c-Fos/AP-1. These results suggest that AP-1 is a major regulatory factor for cell cycle progression of B cells activated with LPS.