On the left side of Hensen’s node, Sonic hedgehog (Shh) activates Cerberus, which stimulates BMPs to induce the expression of Nodal

TLS Online TPP Program

#Id: 10479

#Unit 4. Cell Communication and Cell Signaling

Loss-of-function mutations in PTC1 permit cell

proliferation in the absence of an Hh signal

TLS Online TPP Program

#Id: 10480

#Unit 4. Cell Communication and Cell Signaling

Multi-hit model

LOF mutations in the tumor suppressors APC and p53 and GOF mutation in the oncogene K-RAS establishing that multiple mutations in the same cell are needed for the cancer to form.

TLS Online TPP Program

#Id: 10481

#Unit 4. Cell Communication and Cell Signaling

p53

tumor-suppressor gene 

arrest of cells with damaged DNA

TLS Online TPP Program

#Id: 10482

#Unit 4. Cell Communication and Cell Signaling

p53

extremely unstable protein and generally does not accumulate to high enough levels to stimulate transcription under normal conditions

TLS Online TPP Program

#Id: 10483

#Unit 4. Cell Communication and Cell Signaling

MDM2

catalyzes the ubiquitinylation of p53 & targeting it for proteasomal degradation

TLS Online TPP Program

#Id: 10484

#Unit 4. Cell Communication and Cell Signaling

Rapid degradation of p53 is inhibited by ATM and ATR, after DNA damage