|Ph.D Student||Maoz Tsofnat|
|Subject||A Genetic Analysis of the Apoptotic Pathway Induced by|
Adenovirus E4orf4 Protein
|Department||Department of Medicine||Supervisor||Professor Tamar Kleinberger|
Adenovirus E4orf4 protein is a multifunctional viral regulator. This protein kills oncogenically-transformed cells, but does not kill normal cells. Furthermore, cell death is induced by a mechanism that does not involve the tumor suppressor p53. As a result, E4orf4, can potentially serve as a powerful tool in cancer therapy. Our laboratory is involved in ongoing studies to understand the mechanisms underlying cell killing by E4orf4.
In searching for a system that will facilitate a genetic
analysis of the E4orf4 apoptotic pathway, we carried out experiments in the
yeast S. cerevisiae.
The work in yeast showed that E4orf4 induced growth arrest, leading to cell death, and these events required the presence of PP2A. Moreover, an E4orf4 mutant that did not bind PP2A and did not induce apoptosis in mammalian cells, did not induce growth arrest and cell death in yeast. Thus, the E4orf4-activated pathway has conserved properties in yeast and mammals, and yeast may serve as a genetic tool to identify at least some of its components.
We have mutagenized yeast DNA using a transposon library prepared in bacteria, and isolated YND 1 gene that contributes to E4orf4 toxicity. A deletion mutant of this gene was resistant to E4orf4, and when the wild type Ynd1 was reintroduced into the yeast cells, E4orf4 toxicity was restored. YND 1 is genetically interacts with PP2A, but is not a downstream effector of the E4orf4-PP2A complex. The protein encoded by this gene physically interacts with E4orf4 and genetically interacts with cell cycle.
The role of the mammalian homolog of this gene in E4orf4-induced apoptosis has further to be investigated.