Studies of initiation factors in protein synthesis of host liver and transplantable hepatoma.

The activity of initiation factors obtained from host livers and transplantable H5123 hepatomas of Buffalo rats was investigated using an in vitro assay of protein synthesis. Initiation factors obtained by washing ribosomes with l M KC1, KCl-washed ribosomes, 60 S and 40 S ribosomal subunits, and transferases were prepared from liver and from tumor. The activity in polyuridylic acid [poly(U)]-directed polyphenylalanine synthesis and in the binding of phenylalanine-tRNA-14C and methionyl-tRNA-14C to 40 S ri bosomal subunits at low Mg2+ concentrations was meas ured. Using a system requiring initiation factors, highsalt-washed ribosomes, transferases, and poly(U), initiation and subsequent synthesis of polyphenylalanine chains were found to increase when initiation factors from tumors were used in comparison to initiation factors from host livers. Studies on initiation factors-promoted binding of aminoacyl-tRNA's to 40 S small ribosomal subunits