Translational efficiency of cMyc mRNA in Burkitt lymphoma cells.

The translational efficiency of cMyc mRNAs was assessed in a variety of cell lines: HeLa cells and Epstein-Barr virus-transformed lymphocytes, both of which contain only the germ line cMyc allele; Daudi, a Burkitt cell line containing a translocated cMyc gene with no apparent alteration; and P3HR-1, a Burkitt line in which the 5' end of the translocated cMyc gene has been altered by the chromosomal translocation. Translational efficiency was inferred by measuring the number of ribosomes associated with the cMyc mRNA, using a procedure by which individual polysomal fractions were analyzed by blot hybridization. Since polysome size is a function of the length of the translated sequence as well as the rate of initiation of protein synthesis, we also determined the number of ribosomes associated with a control mRNA (alpha tubulin) which codes for a protein of similar size to cMyc. We found that the cMyc mRNA was associated with a number of ribosomes comparable to that associated with alpha tubulin mRNA in all the cell lines tested.