Question

Which of the following could cause a lymphoma? Choose ONE of the below and explain your choice in 2-3 sentences.

Explanation 1: A mutation in the Rb gene causing a single amino acid change in the Rb protein that prevents it from being recognized by Rb kinase

Explanation 2: A mutation that causes p53 to be constitutively expressed

Explanation 3: An incorrectly spliced transcript from the E2F gene that results in an early stop codon in the mature mRNA

Explanation 4: A missense mutation that changes the shape of p53 and prevents it from binding to an enhancer for a G1 arrest protein gene

Answer 1

Explanation 4: A missense mutation that changes the shape of p53 and prevents it from binding to an enhancer for a G1 arrest protein gene.

p53 mediate G1 cell cycle arrest by down regulating transcription of cell cycle promoting genes and by activating the cell cycle arresting genes. Mutation in p53 causes conformational changes in it and prevents it from binding with cell cycle arrest genes.

explanation 1 is wrong because, phosphorylation of Rb induces cell cycle. If p53 constitutively expresses, it would promote cell death. Thereby no lymphoma will form. Binding of functional E2F is important for the transcriptional activation of genes to promote cell cycle. So both explanation 2 and 3 are also wrong.