Specific regulation of c-myc oncogene expression in a murine B-cell lymphoma.

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Abstract
The c-myc oncogene was implicated in a wide spectrum of B-cell neoplasias. In normal cells, the level of expression of the c-myc gene correlates with growth status. In the present study, the effect of receptor-mediated inhibition of growth on c-myc expression was examined in a B-cell lymphoma. The murine lymphoma line WEHI 231 was characterized as an early B cell; it bears surface-bound IgM and has unrearranged c-myc genes. Following treatment of a WEHI 231 culture with anti-mouse Ig antiserum, the cells undergo one round of division and further proliferation is inhibited. This treatment specifically affected cytoplasmic levels of c-myc mRNA. An initial early increase is followed by a precipitous drop such that by 4 h (after exposure) the amount of c-myc mRNA is below control values by a factor of .apprxeq. 10. The drop in c-myc precedes cessation of DNA synthesis. During the 2- to 4-h period, c-myc mRNA had a maximal half-life of 20-30 min. Even 24 h after anti-Ig exposure, the amounts of most major mRNA, including .mu. H chain and actin, were not significantly altered. Expression of an unrearranged c-myc gene can be selectively responsive to receptor-mediated regulatory events.