c‐Myc Selectively Regulates the Latent Period and Erythroid‐specific Genes in Murine Erythroleukemia Cell Differentiation

During the latent period of murinc erythroleukemia (MEL) cell differentiation, c‐myc levels showed a significant change and the overexpression of the transferred c‐myc gene inhibited the commitment and differentiation of MEL cells, suggesting that c‐Myc may he a key molecule for the commitment. Since c‐Myc may function as a DNA binding transcription factor, we examined whether c‐Myc regulates the latent period genes (hsp and hsc70, MER5, Id and Spi‐1 genes) and the erythroidspecific genes [β‐globin, glycophorin, δ‐aminolevulinic acid synthase (ALAS‐E), GATA‐1 and erythropoietin receptor (EpoR)] in the MEL cell transformant having transferred c‐myc gene. The overexpression of c‐myc gene affected the latent period genes in different ways: hsc and hsp 70 genes and Id gene were positively regulated, while expression of MER5 gene was repressed. While c‐myc is thought to be involved in DNA replication, its overexpression showed no effect on the expression of proliferating cell specific nuclear antigen or DNA polymerase α. The overexpression of c‐myc repressed the expression of glycophorin, ALAS‐E and β‐glohin genes, of the five erythroid‐specific genes, but had no effect on expression of GATA‐1 or EpoR gene. These results suggest that c‐Myc differentially regulates the expression of the latent period and erythroid‐specific genes.