FIG. 1.

Increasing expression of a novel 87-kDa form of Gab1 protein and 4.6-kb mRNA in 10W−1 cells during passages. (A) 10W+8, 10W−1E, and 10W−1L cells were cultured with 10% FBS for 48 to 72 h, and some of the cells were serum starved for 20 h before harvest (10% FBS − lanes). Gab1 was immunoprecipitated (IP) from the lysates of 10W+8, 10W−1E, and 10W−1L cells, analyzed by SDS–8% PAGE followed by anti-Gab1 blotting, and visualized by ECL. Signals at 100 kDa commonly observed among those cells and signals at 87 kDa clearly detected in 10W−1L cells are indicated by arrows as well as signals representing IgG. (B) 10W+8, 10W−1E, and 10W−1L cells were cultured with 10% FBS, and some of the cells were serum starved for 20 h before harvest (10% FBS − lanes). Ten micrograms of total RNA was loaded onto each lane and analyzed for Gab1 mRNA expression. A broad signal around 5.2 kb observed in all cells and an intense signal at 4.6 kb clearly detected in 10W−1L cells are indicated by arrows.