Question

1. How is histone acetylation involved in regulation of gene expression?

2. Describe the difference between promoter and enhancer in eukaryotes.

3. How can a mutation in an insulator region for CTCF binding that controls a topologically associated domain (TAD) contribute to activation of a proto-oncogene thus causing cancer.

4. What is the role of RNA interference?

Answer 1

1.
Histone acetylation involves the covalent addition of an acetyl group to lysine of histones.  
Lysine is normally a positively charged amino acid. So, it binds strongly to the negatively charged DNA molecule. The addition of the acetyl group neutralizes this positive charge and reduces the binding between histones and DNA, which leads to a more open structure of DNA. Open structure of DNA is more accessible to the transcriptional machinery.
Thus, Histone acetylation leads to transcriptional activation.

2.
1. An enhancer is a sequence of DNA that functions to enhance transcription, whereas a promoter is a sequence of DNA that initiates the process of transcription.
2. A promoter has to be close to the gene that is being transcribed while an enhancer does not need to be close to the gene of interest.
3. An enhancer can be upstream or downstream from the site where transcription is initiated while a promoter is always upstream from the site where transcription is initiated.
4. An enhancer binds with transcription factors while a promoter binds with transcription factors and RNA polymerase enzyme.
5. An enhancer works to enhance or increase transcription while a promoter works to initiate the transcription process.
6. Enhancers are thought to be associated with diseases such as type 2 diabetes, cardiovascular disease, and colorectal cancer. Promoters are thought to be associated with diseases such as asthma and beta-thalassemia.

3.
Insulators are short nucleotide sequences that set boundaries between nearby genomic domains. When CTCF binds to an insulator sequence, the conversation between an enhancer and a gene promoter is impeded and transcription of the gene is blocked.
Thus, if a mutation occurs in an insulator region, the transcription of the gene is not blocked even when there is requirement, which results in the activation of a proto-oncogene, thus causing cancer.

4.
A cellular mechanism that use the gene's own DNA sequence of gene to turn it off is known as RNA interference. In this process, RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules.
RNA interference is also known as RNA silencing. It is used to control the activity of certain genes by specifically silencing or deactivating the genes.