Abstract
Cells infected with Friend virus can be induced to erythroid differentiation by culture with 2% dimethylsulfoxide. This study was designed to determine if dimethylsulfoxide causes the expression of erythroid differentiation by an effect on a particular phase of the cell division cycle. The infected cells were synchronized by exposure to 2 mM thymidine. It is shown that dimethylsulfoxide must be present during DNA synthesis (S-phase) and, possibly, shortly thereafter, to induce differentiation assayed by measuring hemoglobin synthesis. In order to achieve an effective intracellular incorporation of dimethylsulfoxide, cells must be exposed to the agent for at least 24-30 hr before the critical S phase. It is suggested that induction of erythroid differentiation in cells infected with Friend virus involves an effect of dimethylsulfoxide, or a metabolic product, that alters the program of transcription, during or immediately after DNA synthesis.