Changes in RNA and protein metabolism preceding onset of hemoglobin synthesis in cultured friend leukemia cells

We have studied the hematopoietic process which is induced by dimethyl sulfoxide (Me₂SO) in the Ostertag FSD-1 line of Friend erythroleukemia (FL) cells and have observed several changes that precede the onset of hemoglobin synthesis at 48 hr. Although cellular viability, mitotic rate, and deoxyribonucleic acid content are unaffected by our induction procedure, the induced cells become progressively smaller, and by 96 hr contain only 55% as much ribonucleic acid and 60-70% as much protein as control cells. The decline in ribonucleic acid content is significant by 24 hr and affects 4S and ribosomal ribonucleic acids in a noncoordinated manner throughout the hematopoietic process. Furthermore, incorporation of radioactive uridine into the 45S precursor of ribosomal ribonucleic acid is specifically inhibited by 1-2 hr after first treating FL cultures with 1% Me₂SO. This earliest known effect of Me₂SO on FL cells is followed by a decline in synthesis of protein. The basic sequence of macromolecular and cell size changes are similar to those that occur during normal erythropoiesis.