Question

3-4 32 degree conditions: (independent variable)

1.This cell line will express p21. a=true and b=false

2.This cell line will contain hyperphosphorylated Rb. a=true and b=false

3. This cell line will have sequestered E2F that does not bind to DNA. a=true and b=false

4. This cell line will have active Cyclin/CDK active for the G1/S transition. a=true and b=false

p53 is expressed and it causes a gel shift for a p53 responsive element for 3-4 cells at 32 degrees

here, a mutant form of p53 was used and they showed that p53 was present and active in the 3-4 cells at 32 degrees. the question is asking if the conditions are true or false if p53 is present

Answer 1

Answer 1. True. If p53 is present then this cell line will express p21 as p53 expression will induce p21 expression to carry out p53 dependent cell cycle arrest.

Answer 2. False. Hyperphosphorylation of Rb causes downregulation of p53 via ARF and MDM2 thus if the cell line is expressing p53, it can be concluded that the phosphorylated form of Rb will not be present.

Answer 3. True. p53 prevents the binding of E2F to DNA by inhibiting the phosphorylation of Rb. If Rb is not phosphorylated then it will be bound to E2F and it will not be released to be able to bind to DNA.

Answer 4. False. If p53 is present this cell line will not have active Cyclin/CDK complex. p53 increases the expression levels of p21 and p27 which are known as CDKI's (CDK inhibitors), p21 and p27 inhibit the cyclins and cause cell cycle arrest.