Question

Question: In eukaryotes, miR-5 is a microRNA with sequence complementarity to the 3’UTR of the mRNA transcript encoded by the ABC gene. The ABC gene encodes for a protein that acts as an allosteric activator of the protein p101. The p101 protein is a histone acetyl transferase (HAT) which is an enzyme that acetylates histones when the protein is in its active form.

A. In a lung cancer cell line, the p101 protein is overly active leading to misregulation of gene expression. In these lung cancer cells which of the following would be a correct prediction in regards to miR-5?          choose ALL that apply,

a. The gene encoding miR-5 is in a region of chromatin with increased DNA methylation

b. The gene encoding miR-5 is in a region with decreased DNA methylation

c. The gene encoding miR-5 is in a region of euchromatin

d. The gene encoding miR-5 is in a region of heterochromatin

e. The miR-5 transcript is translated at high levels

f. The miR-5 transcript is activating translation of the ABC gene

B A different lung cancer cell line is found to have significantly decreasedamounts of histone acetylation. Which of the following could explain why there is decreased histone acetylation in this cell line? choose ALL that apply

a.  increased translation of the p101 protein due to low levels of miR-5

b. decreased translation of the p101 protein due to high levels of miR-5

c. increased translation of the ABC protein due to high levels of miR-5

d. decreased translation of the ABC protein due to low levels of miR-5

e. decreased translation of the ABC protein due to high levels of miR-5

f. the absence of the p101 protein due to miR-5 inhibiting transcription of the p101 mRNA transcript

g. the absence of the ABC protein due to miR-5 inhibiting transcription of the ABC mRNA transcript

Answer 1

a) miR-5 inhibits the expression of the ABC protein by degrading the mRNA of the ABC gene ( miRNA which is completely complementary to the mRNA leads to mRNA degradation using RISC), the ABC protein activates the p101 protein.

in the cell, the p101 is overactive means the ABC gene is translated all the time because miRNA-5 is not transcribed.

DNA methylation prevents transcription of the DNA, euchromatin is loosely packed so genes in the euchromatin is transcribed and heterochromatin is densely packed so genes in the genes in the heterochromatin is not transcribed.

so the answers are

a. The gene encoding miR-5 is in a region of chromatin with increased DNA methylation

d. The gene encoding miR-5 is in a region of heterochromatin

b) histone acetylation is decreased means the p101 is not active, so the levels of ABC protein is decreases, it is due to the increased expression of miRNA-5

so the answer is e. decreased translation of the ABC protein due to high levels of miR-5

for option g, the absence of the ABC protein due to miR-5 inhibiting transcription of the ABC mRNA transcript, the word transcription is used, if that is a typo and the original word is the translation, this option can be one of the answers.

( miRNA-5 does not change the translation of the p101 protein)