Question

Questions 8-9: 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. 8. 8. (1pt) 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] Select all that apply The gene encoding miR-5 is in a region of chromatin with hypoacetylation The gene encoding miR-5 is in a region of chromatin with hyperacetylation The gene encoding miR-5 in a region of euchromatin The gene encoding miR-5 in a region of heterochromatin The miR-5 transcript is translated at high levels The miR-5 transcript is activating translation of the UCD gene

Answer 1

miR-5 inhibits the translation of the UCD mRNA by binding to the 3` end of the mRNA, the UCD gene codes for a protein which is an allosteric activator of p101, in the cancer cells it is found that the activity of the p101 is misregulated, and the p101 is overactive, means the allosteric activator remains bound to the protein always so the UCD mRNA is translated always so the miR-5 which inhibits the translation of the UCD mRNA is not expressed, so the region of the chromatin which codes for the miR-5 is in the heterochromatin state.

histones are positively charged proteins, it is wrapped around the negatively charged DNA using electrostatic interaction, acetylation of the histone decreases the posiitve charge of the protein because the acetyl group is negatively charged, so the interaction between the DNA and the histones decreases and the DNA becomes loosely packed over the histones so the chromatin becomes euchromatin and the genes are expressed.here the expression of miR-5 is decreased so the region of the miR-5 is hyperacetylated.

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

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

9) DNA methylation is decreased, means the p101 is inactive, so the allosteric activator of the p101 is produced at low levels, or absent

so the answer is the absence of UCD protein due to miR-5 inhibiting the translation of the UCD mRNA transcript.