The phosphorylation of retinoblastoma gene product in human myeloid leukenia cells during the cell cycle

Counterflow centrifugal elutriation and immunoblotting techniques were used to study the expression of the retinoblastoma (RB) gene during the cell cycle of BV173 chronic myeloid leukemia (CML) cells. Our data showed that Rb protein started to be phosphorylated at early G1 phase, became hyperphosphorylated when cells progressed to late G1 and S phases during cell cycle, and remained hyperphosphorylated throughout S and G2 M phases. Our data suggest that Rb phosphorylation starts at a more distal point to the G1 S phase boundary in human myeloid leukemia BV173 cells rather than at a point more proximal to the G1 S boundary, as seen in HeLa cells.