Roles of Two Activation Domains in Zap1 in the Response to Zinc Deficiency in Saccharomyces cerevisiae

Abstract

Previous studies suggested that the zinc-responsive Zap1 transcriptional activator directly regulates the expression of over 80 genes in Saccharomyces cerevisiae. Many of these genes play key roles to enhance the ability of yeast cells to grow under zinc-limiting conditions. Zap1 is unusual among transcriptional activators in that it contains two activation domains, designated AD1 and AD2, which are regulated independently by zinc. These two domains are evolutionarily conserved among Zap1 orthologs suggesting that they are both important for Zap1 function. In this study, we have examined the roles of AD1 and AD2 in low zinc growth and the regulation of Zap1 target gene expression. Using alleles that are specifically disrupted for either AD1 or AD2 function, we found that these domains are not redundant, and both are important for normal growth in low zinc. AD1 plays the primary role in zinc-responsive gene regulation, whereas AD2 is required for maximal expression of only a few target promoters. AD1 alone is capable of driving full expression of most Zap1 target genes and dictates the kinetics of Zap1 gene induction in response to zinc withdrawal. Surprisingly, we found that AD1 is less active in zinc-limited cells under heat stress and AD2 plays a more important role under those conditions. These results suggest that AD2 may contribute more to Zap1 function when zinc deficiency is combined with other environmental stresses. In the course of these studies, we also found that the heat shock response is induced under conditions of severe zinc deficiency.

Activation of the Yeast UBI4 Polyubiquitin Gene by Zap1 Transcription Factor via an Intragenic Promoter Is Critical for Zinc-deficient Growth

“…In zap1 mutant cells, UBI4 induction occurs during zinc limitation, but this effect is no longer dependent on the ZREs. This result is consistent with our previous observation that Hsf1 activity is increased in zinc-deficient zap1 mutants, which experience a much greater degree of stress than do wild-type cells (32).…”

Zinc finger protein Loz1 is required for zinc-responsive regulation of gene expression in fission yeast

“…The growing number of unique eukaryotic zinc-regulated factors that have been identified suggests that novel zinc-sensing domains may have evolved independently in different species. Intriguingly, studies with Zap1 have shown that AD1 is plays a primary role in activating genes required to maintain zinc homeostasis, whereas AD2 plays a more major role in gene regulation when zinc deficiency is combined with other environmental stresses (26). Thus, one potential explanation for the diversity in zinc-regulated factors is that each unique factor is able to optimally sense changes in zinc levels under normal and specialized environmental conditions.…”

“…Zap1 contains multiple domains that are independently regulated by zinc (25). These domains include AD1, a transactivation domain that is rich in histidine and cysteine residues, and AD2, a transactivation domain that contains a unique regulatory zinc finger pair motif (26). In mammals, MTF-1 also contains multiple zinc-regulated domains including a zinc-responsive DNA binding domain containing six C 2 H 2 -type zinc fingers (9).…”

The Double Zinc Finger Domain and Adjacent Accessory Domain from the Transcription Factor Loss of Zinc Sensing 1 (Loz1) Are Necessary for DNA Binding and Zinc Sensing

“…Both factors contain multiple zinc-responsive domains. Zap1 contains two transactivation domains that are independently regulated by zinc (9,10). Zinc also inhibits Zap1 DNA binding activity (11).…”