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The Eukaryotic Cell Cycle (PowerPoint)

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					The Eukaryotic Cell Cycle

          刘 雯
Question
• When to initiate replication:S-phase
 entry

• When to begin chromosomal
 condensations :M-phase entry
Control mechanism of S-phase entry

• Start
• Restriction point
• SPF cdc28
       G1 cyclin(CLN1,CLN2,CLN3)
Cdk            cyclin           control phase
S.pombe
cdc2           cdc13            G2     M
S.cerevisiae
cdc28          cln1,cln2,cln3   G1     S
Mammal cells
cdk2           cyclinD1,D2,D3   G1
               cyclinE          G1     S
               cyclinA          S
cdk4           cyclinD1,D2,D3   G1
cdk5           cyclinD1,D2,D3   G1
cdc2(cdk1/p34) cyclinA,B        G2     M
Control mechanism of S-phase entry
have been associated with SPF
• Regulation of transcription factor activity

• Regulation of replication initiation factor
  activity
Four factors related to the entry into
M-phase
• Mass factor:The accumulation of a specific
  cellular mass is a factor for somatic cells.
• Growth rate factor:Some cells need to obtain a
  specific growth rate for mitosis to begin.
• Time factor:The time between successive M-
  phase appears to be controlled by timer or
  oscillator genes.
• Replication factor: The entry into the M-phase
  also requires complements of the S-phase.This
  insures that daugher cells received complete DNA.
Cdk            cyclin           control phase
S.pombe
cdc2           cdc13            G2     M
S.cerevisiae
cdc28          cln1,cln2,cln3   G1     S
Mammal cells
cdk2           cyclinD1,D2,D3   G1
               cyclinE          G1     S
               cyclinA          S
cdk4           cyclinD1,D2,D3   G1
cdk5           cyclinD1,D2,D3   G1
cdc2(cdk1/p34) cyclinA,B        G2     M
 Mechanism regulating entry into the M-phase
 is common to all eukaryotic cell, the key
 features of the process are as follows:
• The protein kinase activity of p34cdc2 is central to
  the model.This protein is thought to phosporylate
  key proteins that lead to the major events in the
  M-phase.
• The second key protein is cycline that complexes
  with p34cdc2 to form the MPF.
• Timing of the M-phase entry is associated with
  two other protein kinases and accumulation of
  p80cdc25
• p13suc1 interacts with p34cdc2 and may be
  involved in its rephosphorylation at the end of the
  M-phase
Cellular events have been associated
with the onset of the protein kinase
activity of the cdc2 product
• Chromosomal condensation
• Cytoskeletal reorganization
• Nuclear envelope breakdown
• Cell shape changes
    The key substartes of p34cdc2 protein kinase
• Histone H1-the phosphorylation of this protein
    may be important for chromosmal
•   Other DNA binding proteins that need to be
    released for chromosomal condensation to occur
•   Centrosomal protein-these protein are associated
    with centrioles,the organizing center of the cell for
    microtubules associted with the cytoskeleton
•   Lamin-this is a protein associated with the
    nuxlaar envelope
•   P60src-phosohorylation of the mitotic specific sites
    of this protein may influence the cytoskeleton and
    lead to changes in the cell shape
What is check point?
Is enviroment favorable?
• Growth factor and growth factor
  receptor
• Chalone
• Oncogene and tumor suppressor gene
• Second signal

				
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posted:4/25/2011
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