Oncogenes and Cell Cycle (Herschman) Flashcards Preview

Block 1 lectures > Oncogenes and Cell Cycle (Herschman) > Flashcards

Flashcards in Oncogenes and Cell Cycle (Herschman) Deck (10):
1

What makes v-erbB a dominant oncogene?

It is only the C terminus of the EGF receptor so has no growth factor binding domain and is thus constitutively active

2


What makes PDGF a dominant oncogene?


If a cell is infected with an RNA tumor virus, PDGF is expressed INSIDE the cell and this autocrine signaling can lead to cancer

3


What makes v-fos and v-jun dominant oncogenes?


If cell is infected with RNA tumor virus, the transcription factors v-fos and v-jun are expressed and transcribe genes that can lead to cancer

4


Are there dominant oncogenes in the Ras pathway?


Yes: ligand itself, receptor, Ras, Raf, transcription factors

5


Normal pathway leading to Ras signaling

Growth factor ligand binds to receptor → receptor is phosphorylated → now Grb2, which is attached to GNEF via SH3 domains, recognizes and binds phosphorylated receptors → Ras binds GNEF → binding causes Ras to release GDP and take up GTP → Ras-GTP is now active and can signal → GAP binds Ras to help it cleave GTP to GDP and Ras is now inactive

6

What does active Ras (Ras-GTP) do?


Activates a protein kinase cascade:

Ras → RAF → MAPKK → MAPK → nucleus to phosphorylate transcription factors, making them active

7

What is the difference between viral Ras and cellular Ras?


Viral Ras cannot interact with GAP, so it is locked in the "ON" position

8

Can single point mutations in genes contribute to cancer?


Yes

1) Ras unable to bind GAP

2) G alpha subunit leads to endocrine tumors

3) bRaf mutation in 2/3 of melanoma tumors (furthermore, 50% of patients have exact same mutation)

9


Is Ras mutated in many human cancers?


Yes, 1/3 of human cancers have Ras mutation

10

Diagram all the steps of the Ras pathway. From initation to gene expression.

A image thumb