Question

In eukaryotes, miR-5 is a microRNA with sequence complementarity to the 3’UTR of the mRNA transcript encoded by the UCD gene. The UCD gene encodes for a protein that acts as an allosteric activator of the protein p101. The p101 protein is a DNA methyltransferase (DNMT) which is an enzyme that methylates DNA 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, note that incorrect selections will deduct points]
A) The gene encoding miR-5 is in a region of chromatin with hypoacetylation
B) The gene encoding miR-5 is in a region of chromatin with hyperacetylation
C) The gene encoding miR-5 in a region of euchromatin
D) The gene encoding miR-5 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 UCD gene
B) A different lung cancer cell line is found to have significantly decreased amounts of DNA methylation. Which of the following could explain why there is decreased DNA methylation in this cell line? [choose ALL that apply, note that incorrect selections will deduct points]
A) increased amounts of the p101 protein due to low levels of miR-5
B) increased amounts of the UCD protein due to high levels of miR-5
C) decreased amounts of the UCD protein due to low levels of miR-5
D) the absence of the UCD protein due to miR-5 inhibiting translation of the UCD mRNA transcript
E) the absence of the p101 protein due to miR-5 inhibiting transcription of the p101 mRNA transcript

Answer 1

In lung cancer cells with overly active p101 protein, the gene encoding miR-5 is likely in a region of heterochromatin. In a different lung cancer cell line with decreased DNA methylation, the decrease could be explained by increased UCD protein levels due to high levels of miR-5 and the absence of p101 protein due to miR-5 inhibiting transcription of p101 mRNA.

Step-by-step explanation:

In the lung cancer cell line where the p101 protein is overly active, a correct prediction in regards to miR-5 would be that the gene encoding miR-5 is in a region of heterochromatin. This is because the protein p101, which is an allosteric activator of p101, is overly active in these cells, leading to misregulation of gene expression. Heterochromatin is typically associated with gene repression, so it is likely that the miR-5 gene would be in a region of heterochromatin.

In a different lung cancer cell line with significantly decreased DNA methylation, the following could explain the decrease:

• Increased amounts of the UCD protein due to high levels of miR-5
• The absence of the p101 protein due to miR-5 inhibiting transcription of the p101 mRNA transcript

Answer 2

A) A) The gene encoding miR-5 is in a region of chromatin with hypoacetylation.

D) The gene encoding miR-5 in a region of heterochromatin.

B) D) the absence of the UCD protein due to miR-5 inhibiting translation of the UCD mRNA transcript

Step-by-step explanation:

MicroRNAs (miRNAs) are small regulatory RNA sequences (approximately 20-24 nucleotides in length) that regulate gene expression by RNA interference (RNAi) mechanisms. These sequences (miRNAs) bind by base complementarity to messenger RNAs and thus inhibit protein translation and/or trigger mRNA degradation. In this case, miR-5 binds to the 3’UTR of the mRNA transcript of the UCD gene, thereby inhibiting/slowing protein UCD synthesis. The UCD protein is an allosteric regulator that binds and activates the expression of the p101 protein, thereby the miR-5 RNAi pathway also indirectly decreases the expression of the p101 gene. Moreover, hypoacetylation is an epigenetic mark generally associated with gene silencing (heterochromatin is a transcriptionally inactive state of chromatin).