FURTHER BIOCHEMICAL STUDIES ON “MELANOTIC TUMOR” AND “FRECKLED-TYPE MELANOTIC TUMOR” IN D. MELANOGASTER

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Protein fractions of the Drosophila larva in tu and Oregon R strains by means of an ammonium sulfate were studied by Tiselius-electrophoresis and by ultraviolet analysis, and it was found that a qualitative difference between tu and the control was electro-phoretically observed in a fraction (F-3) of five fractions obtained from the 12000g.- supernatant of larva-homogenates treated with an ammonium sulfate (2.8M in final concentration); namely, the tu material has only one peak in a direction “up” although the control shows two little peaks. A quantitative difference of ultraviolet-absorption at around 285mμ was also observed between tu and the control in a fraction (F-2).
On the other hand, tumor-inducibility of “Freckled-type” melanotic tumor, F-type, was detected by injection of three fractions (F-1, F-2, and F-3) separated from these larva-homogenates by DEAE-cellulose column-chromatography (NaCl-linear concentration gradient-elution), into both pre-third instar larva of Varese (non-tumor strain) and Chieti-v (a strain with low tumor incidence of ordinal melanotic tumor, M-type). The results showed that the inducibility of F-type tumor in Varese and the relatively higher inducibility of M-type tumor might be in the F-2. Further, the F-2 was checked for the existence of nucleic acids by ultraviolet analysis, orcinol and diphenylamine reactions, and ³²P_i-incorporation experiment. However, negative results were obtained. From these experimental results and the previous reports (Kanehisa 1960b), it is suggested that the F-type tumor-inducible factor (or factors) may not be a substance with nucleic acids but a kind of biochemically active protein which contains tryptophan or its derivative, and that such a specific factor may not specifically be different from a factor for M-type tumor and its specificity for F-type tumor may depend on hereditary nature of the host-itself responsible for the factor.