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Comparison of in Vivo Translation Rates and Messenger RNA Levels of _2U-Globulin in Rat Liver and Morris Hepatoma 5123D¹

Institute of Cancer Research and Department of Biochemistry, Columbia University, New York, New York 10032

The synthesis of the male rat hepatic protein _2U-globulin has been examined in Morris hepatoma 5123D and male host liver using pulse incorporation of labeled amino acids in vivo, followed by immunoprecipitation of the newly synthesized _2U-globulin from the soluble protein fraction of liver and hepatoma tissue. It was found that no _2U-globulin synthesis occurs in hepatoma tissue, whereas host liver synthesizes _2U-globulin at a normal level (0.9 to 1.0% of total hepatic protein synthesis). A variety of liver-derived cell culture lines also did not have _2U-globulin synthesis.

The level of the specific mRNA coding for _2U-globulin can be quantitated using in vitro translation of polyadenylate-containing RNA in a Krebs II ascites cell-free translational system, followed by immunoprecipitation of the _2U-globulin synthesized in vitro. Using this technique, it was found that host liver contained _2U-globulin mRNA at normal levels, whereas hepatoma tissue contained no detectable mRNA coding for this protein. Thus, _2U-globulin synthesis is deleted in the minimal-deviation hepatoma 5123D as a consequence of the inability of that tissue to produce functional mRNA coding for _2U-globulin. The implications for the regulation of gene expression in malignant cells are discussed.

¹ Supported by Grants CA-02332, CA-10729, and CRTY 05011 from the NIH.

² Present address: Max-Planck-Institut fur Molekulare Genetik, 1 Berlin 33, Ihnestraße 63–73, West Germany.

³ Present address: Department of Biochemistry, Howard University, College of Medicine, Washington, D. C.

⁴ To whom requests for reprints should be addressed.

Received 3/ 3/76. Accepted 6/15/76.