Differential expression of the normal and of the translocated human c-myc oncogenes in B cells.
We have investigated whether the translocated and the untranslocated human c-myc oncogenes of Burkitt lymphoma cells are equally or differentially expressed in host mouse B cells. The human c-myc mRNA levels in somatic cell hybrids between mouse plasmacytoma cells and Burkitt lymphoma cells with either the t(8;14) or the t(2;8) chromosome translocation were determined by using the nuclease S1 protection procedure. Although both the human parental lines and the hybrid cells carrying the translocated c-muc oncogene expressed high levels of human specific c-myc transcripts, the hybrid cells carrying the untranslocated c-myc gene on normal chromosome 8 did not contain human specific c-myc mRNA. These results suggest that the translocated human c-myc oncogene has escaped the normal transcriptional control to which the untranslocated c-myc gene remains subjected. This interpretation is also supported by the finding that the expression of the c-myc genes of lymphoblastoid cells and of HL-60 promyelocytic leukemia cells are repressed when they are transferred into a mouse plasmacytoma background. The ability of the translocated c-myc oncogene to escape the normal transcriptional control occurring in B cells may be important for the expression of B cell neoplasia in mouse and man. We have also transferred the Burkitt 14q+ chromosome carrying a translocated c-myc oncogene into mouse LM-TK- fibroblasts and studied the levels of human c-myc transcripts in the hybrids. Because the levels of human c-myc transcripts in the fibroblast hybrids are dramatically decreased in comparison to the plasmacytoma hybrids, we conclude that the levels of transcripts of the translocated c-myc oncogene depend on the differentiated state of the cells harboring the translocated chromosome.
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D002051:Burkitt Lymphoma / Q000235:genetics; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells; D004262:DNA Restriction Enzymes; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D006822:Hybrid Cells / Q000502:physiology; D007527:Isoenzymes / Q000235:genetics; D007945:Leukemia, Lymphoid / Q000235:genetics; D051379:Mice; D009693:Nucleic Acid Hybridization; D009857:Oncogenes; D010954:Plasmacytoma / Q000235:genetics; D014178:Translocation, Genetic
D007527:Isoenzymes; D004262:DNA Restriction Enzymes