EXPRESSION, REGULATION, AND CHROMOSOMAL LOCALIZATION OF THE MAX GENE

The Max gene encodes a protein that interacts specifically with the My c protein to form a heterodimer with high affinity for the specific co gnate DNA binding site of Myc. Here we examine the expression of Max R NA in comparison to Myc RNA during cell growth and differentiation. Tw o species of RNA, a major 2.0- and a minor 1.7-kilobase species, hybri dized specifically to a Max cDNA probe in all human and murine cell li nes that were tested. Unlike Myc, the steady-state level of Max RNA is not significantly modulated with respect to proliferation or differen tiation. Max RNA is expressed in quiescent BALB/c 3T3 cells and is mod estly increased 3 h after addition of serum to the quiescent cells. In contrast to Myc RNA, Max RNA does not decline immediately upon induct ion of differentiation of HL60 cells by dimethyl sulfoxide, and only a modest decrease of Max RNA was observed 72 h after induction of diffe rentiation. Unlike Myc RNA, Max RNA is relatively stable with a half-l ife of > 3 h and, therefore, does not exhibit the characteristic short half-life of RNAs encoded by most immediate early genes. The human Ma x gene was localized to chromosome 14, band q23. With respect to the r ecurring abnormalities in human tumors, this region of chromosome 14 i s involved in deletions in B-cell chronic lymphocytic leukemia and mal ignant lymphomas and in the 12;14 translocation in uterine leiomyomas.