Figure 14.

Summary of Gln3 responses to alteration of residues 64–73 (pRR752) or DNA binding site residues 332–345 (pRR787). Gln3_64–73 is required for nuclear Gln3-Myc¹³ export under all growth conditions (pRR752). When intracellular glutamine levels are high, Gln3-Myc¹³ can exit the nucleus without binding to its promoter target DNA sequence, i.e., in the absence of a functional Gln3 DNA binding site (pRR787). When glutamine levels are low, Gln3-Myc¹³ can exit the nucleus only if the residues required for DNA binding are intact and DNA binding can occur. Repressive nitrogen sources that prevent nuclear Gln3 entry, e.g., asparagine and glutamate + ammonia, are not sufficient to permit nuclear Gln3 export in the absence of a functional DNA binding site.