IN S I T U LOCALIZATION OF GLOBIN MESSENGER RNA FORMATION II. After Treatment of Friend Virus-Transformed Mouse Cells with Dimethyl Sulfoxide

Globin messenger R N A ( m R N A ) levels in Fr iend v i rus t rans formed mouse cells have been es t imated by in situ hybr id iza t ion of D N A copy ( c D N A ) to fixed p repa ra t ions of cells and by hybr id iza t ion of c D N A to ext rac ted cy top lasmic R N A in true solution. The results obta ined by both methods agree in showing that a low level of globin m R N A can be detected in un t rea ted Fr iend cells. The levels of hemoglob in and globin m R N A have also been cor re la ted af ter t r ea tmen t of Fr iend cells with d imethy l sulfoxide ( D M S O ) . The results obta ined by both exper imen ta l approaches show tha t there is a m i n i m u m per iod of t r ea tmen t with D M S O required in o rder that Fr iend cells may become hemoglobin ized , and tha t this per iod coincides with the t ime when globin m R N A accumula tes . Moreover , b romodeoxyur id ine prevents both hemoglobin and globin m R N A accumula t ion . In the accompanying paper (1) in situ hybridization of globin DNA copy (cDNA) to fetal liver was used to elucidate the process of globin messenger RNA (mRNA) formation in erythroid precursor cells. The essential conclusions were also confirmed by conventional hybridization studies. In the present paper, the same dual approach is applied to a different experimental system in which hemoglobin synthesis in Friend virus-transformed mouse cells is induced by treatment with dimethylsulfoxide (DMSO) (2). The results obtained by in situ and conventional hybridization agree in showing that there is a minimum period of treatment with DMSO required in order that globin mRNA and hemoglobin may accumulate. M A T E R I A L S AND METHODS