Epidermal Growth Factor Signalling Pathway Question?
I'm going through medical exam sample papers and am really stuck on one question, which involves a diagram and multiple choice answers. I've searched surrounded by many textbooks and online, and yet can't take much info on it.
More than one answer may be correct for any line.
Diagram: http://i287.photobucket.com/albums/ll160…
The diagram above illustrates a signalling pathway that is hyperactive within breast cancer cells. Each label A-L indicates a protein. Identify the protein(s) that are described below.
1. One protein whose absence will tend to end in cells to divide (that is, the product of a tumour suppressor gene).
2. One protein that is not synthesized by the parental, non-tumour cells but which is regularly expressed by breast cancer cells.
3. One protein that binds to DNA. (I believe this is L, but maybe others also?)
4. One protein that is regularly mutated in cancers in such a track that its ability to activate the downstream target is maintained for a much longer time than is the defence for the normal protein.
5. One or more proteins (without kinase catalytic activity) that bind to a second, target protein. The target protein, a kinase, is inactive unless the indicated protein(s) is/are found.
Any help, or a point within the right direction, would be greatly appreciated!
Answers:
1. K - Rb is one of the classic example of a tumor suppressor
2. Not sure about this one, but I'd guess A cause there's no real explanation to have EGF in tissue that's not actively dividing?
3. L works, E2F is a transcription factor so it needs to bind to DNA
4. E - Ras fits this, it's a GTPase that deactivates itself, and this function is recurrently lost due to a mutation so it stays active (another classic example)
5. I - CDKs (cyclin dependent kinases), as their name implies, don't do anything unless nearby is a cyclin bound. A might also be correct, as its receptor (EGFR) is also a kinase (it kinases itself, but i guess that still counts). The MAP kinases probably don't fit here because the question specifies "without catalytic activity." Source(s): Lots of throbbing cancer/molecular bio classes...
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More than one answer may be correct for any line.
Diagram: http://i287.photobucket.com/albums/ll160…
The diagram above illustrates a signalling pathway that is hyperactive within breast cancer cells. Each label A-L indicates a protein. Identify the protein(s) that are described below.
1. One protein whose absence will tend to end in cells to divide (that is, the product of a tumour suppressor gene).
2. One protein that is not synthesized by the parental, non-tumour cells but which is regularly expressed by breast cancer cells.
3. One protein that binds to DNA. (I believe this is L, but maybe others also?)
4. One protein that is regularly mutated in cancers in such a track that its ability to activate the downstream target is maintained for a much longer time than is the defence for the normal protein.
5. One or more proteins (without kinase catalytic activity) that bind to a second, target protein. The target protein, a kinase, is inactive unless the indicated protein(s) is/are found.
Any help, or a point within the right direction, would be greatly appreciated!
Answers:
1. K - Rb is one of the classic example of a tumor suppressor
2. Not sure about this one, but I'd guess A cause there's no real explanation to have EGF in tissue that's not actively dividing?
3. L works, E2F is a transcription factor so it needs to bind to DNA
4. E - Ras fits this, it's a GTPase that deactivates itself, and this function is recurrently lost due to a mutation so it stays active (another classic example)
5. I - CDKs (cyclin dependent kinases), as their name implies, don't do anything unless nearby is a cyclin bound. A might also be correct, as its receptor (EGFR) is also a kinase (it kinases itself, but i guess that still counts). The MAP kinases probably don't fit here because the question specifies "without catalytic activity." Source(s): Lots of throbbing cancer/molecular bio classes...
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