Transcriptional Regulation Of Copper-sensing Transcription Factor MAC1

Copper is an indispensible trace element in human. This is mainly duo to copper serves as cofactor to several important enzymes. Therefore, human body must absorb sufficient copper to support life. It is known chronic copper deficiency can lead to anemia. However, excess copper is toxic to human and other living organisms. Copper toxicity is believed to be linked to cancers and neurodegeneration diseases. Because of the biological characteristics of copper, biological organisms must tightly control the cellular copper concentration to maintain at a level that is not too high and not too low. How cells prevent excess copper accumulation has been thoroughly investigated and relevant genes and their regulatory mechanisms have been elucidated. It is known that under copper deficiency, cells activate the copper transporting machinery. However, how cells sense the lack of copper, what is the nature of this biological signal and how the signal is transduced to activate copper uptake have not been fully determined. Understanding these questions can help to determine how nutrients regulate cells growth, which could provide guidance to the nutrient-starvation therapy for cancer treatment.The current thesis research, using yeast as a model organism, studies transcriptional regulation of copper sensing transcription factor Mac1. MAC1 is known to activate copper uptake machinery in yeast when copper is lacking. Determining how MAC1 transcription is regulated will help to determine how cells sense copper deficiency and how this signal is transduced. Previously, our laboratory has identified several cis-acting elements in MAC1 promoter, including the binding sites for Pho2, Gcn4, Ace2 and Swi5 transcription factors. Using gene deletion method, the current these aims to ascertain whether these genes play important roles in MAC1 transcription regulation. PHO2 is known to play an important role phosphate homeostasis, GCN4 in amino acid metabolism and ACE2 and SWI5 in cell cycle. The current thesis studies found that deletion of PHO2 gene reduced MAC1 expression and inhibited yeast growth under copper demanding conditions. Deletion of ACE2 or SWI5 had similar effects on yeast growth. However, deletion of GCN4 had opposite effect as compared to that of PHO2, ACE2 or SWI5 deletion. These results demonstrate that Pho2, Gcn4, Ace2 and Swi5 play important roles in MAC1 transcription regulation. The data also reveal that signaling copper deficiency is intimately linked with cellular phosphate and amino acid homeostasis as well as cell cycle.