Association of distinct yeast Not2 functional domains with components of Gcn5 histone acetylase and Ccr4 transcriptional regulatory complexes.

The NOT genes were originally identified in a yeast genetic screen that selected mutations resulting in increased utilization of a non-consensus TC TATA element of the HIS3 promoter. Here, we present evidence that the N-terminus of Not2 interacts with components of the Ada/Gcn5 histone acetyltransferase complex. Loss of this interaction either through abrogation of Not2 N-terminal function or deletion of ada2 or gcn5 results in derepression of the HIS3 TC element. This suggests that association of Not2 with the Ada/Gcn5 histone acetyltransferase complex is involved in regulation of the HIS3 promoter. Association between the Not and CCR4 transcriptional regulatory complexes has also been observed recently. Our phenotypic analyses suggest that these CCR4-related Not2 functions are mediated by a functionally independent domain of Not2 that includes the highly conserved C-terminus. Chimeric proteins containing the yeast Not2 N-terminus fused to the human C-terminus function in yeast, suggesting that the Not2 C-terminus represents a distinct modular domain whose function is conserved between higher and lower eukaryotes.