cell cycle control system in yeast cell

2. YEAST CELL CYCLE
 The cell cycle is an series of macromolecular event
that leads to cell division and the production of two
daughter cells that are identical to parental cell.
 Yeast cell cycle is controlled by specific kinases,
which contains cyclin and CDK as subunit.
 Cdc 25, cdc13, wee1, CAK, cdc 2 are the enymes
that controls yeast cell cycle.

3. CONTROL OF G1 - S PHASE
STEP 1:
1. phase cyclin CDK complexes
begin to accumulate in
G1,but inhibited by sic1.
2. This prevents DNA
replication.
3. G1 cyclin CDK complex
assembled in late G1
phosphorylate sic 1.

4. STEP 2:
Proteosomal degradation by ubiquitin ligase.

5. STEP 3:
Active s phase cyclin CDK complexes
initiate DNA replication.

6. REGULATION OF MPF
 Interaction of mitotic cyclin with cdk forms MPF
 CDK phosphorylated at two sites
a) Y15 by wee1
b) T161 by CAK
 Dephosphorylated on Y15 by cdc25 yields active MPF.

8. VARIATION OF CDC2 ACTIVITY