Factors controlling the DNA-synthesis in 3T3 and EAT cells.

Beta globulins, (Cohn Fr. III), are a major source of molecules affecting the DNA-synthesis of 3T3 and EAT cells. Growth inhibitors for both cell types, chromatograph at the same position, corresponding to a mol. wt of about 50,000. A very basic, (pI 10.1), factor is isolated by gel electrofocusing, which stimulates the DNA-synthesis of 3T3 and EAT cells. Because of its extremely high cationic charge and its adsorption on gels, the estimation of the exact molecular weight and its preparative isolation, becomes very difficult. Some of the above mentioned molecules are heat-stable and express their action even after boiling for 10 min at pH 3.