It does not exist as an independent unit (e.g., analogous to the ribosome), but assembles de novo at the origin for each replication cycle.

TLS Online TPP Program

#Id: 1490

#Unit 4. Cell Communication and Cell Signaling

p53 transcription is upregulated by growth factor stimulation, as the cell begins preparation for its trip through GI and the important GI to S transition.

TLS Online TPP Program

#Id: 1491

#Unit 4. Cell Communication and Cell Signaling

p53 protein product is regulated by a protein called MDM2, which works through a negative feedback loop.

TLS Online TPP Program

#Id: 1492

#Unit 4. Cell Communication and Cell Signaling

MDM2 transcription is increased by p53. 

TLS Online TPP Program

#Id: 1493

#Unit 4. Cell Communication and Cell Signaling

MDM2 inhibits p53  by targeting it to the ubiquitin-dependent proteosomal degradation pathway.

TLS Online TPP Program

#Id: 1494

#Unit 4. Cell Communication and Cell Signaling

DNA damage leads to phosphorylation of MDM2, which inhibits its ability to promote p53 degradation allowing p53 levels to increase.

TLS Online TPP Program

#Id: 1495

#Unit 4. Cell Communication and Cell Signaling

Growth factor stimulation of cell cycle progression leads to an increase in transcription of the p19ARF protein, which inhibits MDM2’s ability to inhibit p53 .