We have studied the presence of high-mobility-group (HMG) chromatin proteins in undifferentiated F9 mouse teratocarcinoma cells and F9 cells, which were induced to differentiate by treatment with retinoic acid and dibutyryl-cAMP for 5 days. Acetic acid/urea-polyacrylamide gel electrophoresis and reversed-phase HPLC revealed that the induced F9 cells contained 77 and 62% less HMG I and HMG Y, respectively, than their untreated counterparts. The relative amounts of two other low-M r HMG proteins HMG 14 and HMG 17 remained essentially unchanged and only a minor decrease was observed in the content of one of the high-M r HMG proteins, HMG 2. The identity of the low-M r HMG proteins was verified by amino acid analysis or partial sequencing. These results suggest that HMG I and HMG Y are HMG proteins specific for undifferentiated cells.
