1. C O R E Y D I L L A R D
Saccharomyces cerevisiae:
Providing Insight Into Human
Tumor Suppressor Genes

2. Saccharomyces cerevisiae
(Yeast)
 Model organism for
humans
 Eukaryotic
 Gene and Protein
homologs
 Quick replication
 Haploid or Diploid form

3. TEP1 (YNL128W)
 Saccharomyces cerevisiae homolog for
PTEN/MMAC1/TEP1
 Yeast strains deleted for TEP1:
 Show no phenotype in haploids
 Diploids exhibit resisitance to phosphatidylinositol-3-
phosphate kinase inhibitor
 Wortmannin
 Lithium ions (LY294002)

4. PTEN/MMAC1/TEP1
 PTEN
 Phosphatase and tensin homolog
 Tumor suppressor protein
 Modifies other proteins and fats by removing phosphate groups
 MMAC1
 Mutated in multiple advanced cancers
 TEP1
 Tensin-like phosphatase

5. PTEN/MMAC1/TEP1
 Health conditions associated with mutations:
 Bannayan-Riley-Ruvalcaba syndrome
 Formation of hamartomas and other tumors
 Cowden syndrome
 Formation of hamartomas and increased risk of developing breast,
thyroid, and endometrial cancer
 Proteus syndrome
 Asymmetric overgrowth of the bones, skin, and other tissues
 Cancers
 Prostate, endometrial, and melanoma
 Glioblastomas and astrocytomas

6. PTEN in PI3-Kinase Pathway
 The PI3-kinase pathway is essential for cell
metabolism, proliferation, cell-cycle progression, and
survival
 PTEN is responsible for directly inhibiting PIP3
 Unrestrained signaling can lead to lymphomas and
leukemia

7. Akt/PKB
 Serine/threonine protein
kinase
 Inactivates multiple
targets by
phosphorylation
 PIP3 and PI3-kinase
 Recruitment of Akt and
PDK1
 Akt and PDK1
 PH domain docking sites

8. PI3K/Akt Signaling Pathway

9. Resistance to PI3-Kinase Inhibitors
 Various concentrations
 Lithium ions
 Wortmannin
 Haploid
 Weak to no phenotype
 Diploid
 Strong phenotype
(resistance)
 Growth inhibition

10. Lifespan Determination
 Cells from liquid culture to plate
 Isolation of buds from mother cells
 Compare divisions between knockout
haploid/diploid strains
 Mean lifespan
 Is TEP1 responsible for aging process?

11. TEP1 in Sporulation
 Determine cells completing meiosis I and II
 Fluorescence microscopy
 DNA-specific dye, DAPI (4’, 6-diamidino-2-phenyl-indole)
 TEP1 absence effect?
 None on spore viability
 High amount of damaged asci and released spores in diploid

12. Sporulation/Fluorescence

13. Spore Wall Formation
 Dityrosine (fluorescent) during ascus maturation
 Component of spore wall
 UV light or fluorescence microscopy
 Mutant
 Accumulated earlier, final level lower
 Wild type
 Accumulated slower, final level higher
 Why?
 Cellular fractionation

14. Summary
 Yeast – Maturation of spore wall + meiotic cell
Human – Extracellular matrix + epithelial cell
 Carcinogenesis
 Alteration of pathways compensate for absence of
TEP1
 Possibly restore phosphatidylinositols to normal levels
 TEP1 is involved in the phosphatidylinositol pathway
in yeast

15. References
 "PI3K / Akt Signaling Pathway." Welcome to CST.
Ed. Michael Scheid. N.p., Sept. 2007. Web. 3 Nov.
2014.
 Heymont, Jennifer, Ludmilla Berenfeld, Jennifer
Collins, and Alexandra Kaganovich. "TEP1, the Yeast
Homolog of the Human Tumor Suppressor Gene
PTEN/MMCAC1/TEP, Is Linked to the
Phosphatidylinositol Pathway and Plays a Role in the
Developmental Process of Sporulation." PNAS 97.23
(2000): 12673-2677. Print

16. THANK YOU! QUESTIONS?