Molecular basis of reduced albumin synthesis in Morris hepatoma 7777

Abstract

The level of albumin mRNA in the normal Buffalo rat liver and Morris hepatoma 7777 was compared by molecular hydridization with albumin complementary DNA (cDNA) and translational assays. Albumin mRNA was 10% of the total rat liver poly(A)-containing RNA population but reduced approximately 4-fold in the case of Morris hepatoma 7777. An equivalent decrease of albumin mRNA activity in the hepatoma was detected by translation in a mRNA-dependent cell-free protein-synthesizing system. A proportional increase in total hepatoma poly(A)-containing RNA was not observed, indicating that there was a true 4-fold reduction of albumin synthesis in the hepatoma. DNA excess hybridization with albumin cDNA did not reveal any apparent change in albumin gene frequency in the hepatoma compared to normal liver. DNA copies of total liver and hepatoma poly(A)-containing RNA were synthesized and employed in homologous and heterologous hybridization reactions. Analyses of these reactions showed a high degree of homology between the poly(A)-containing RNA of the liver and hepatoma, with some differences in the relative sequence abundancy. Qualitative differences were detected in hepatoma 7777 consistent with the concept of alterations in the control of gene expression on neoplastic transformation.