Gene regulation in eukaryotes I: Transcriptional and translational regulation - DNA methylation

13 important questions on Gene regulation in eukaryotes I: Transcriptional and translational regulation - DNA methylation

Via what enzyme occurs DNA methylation in eukaryotes?

Via DNA methyltransferase.

To which base is the methyl group attached?

To cytosine.

What are CpG islands?

A dinucleotide of C and G, connected by a phosphodiester linkage.
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What is full methylation?

When the C of the one strand and the C on the other strand in a CpG island are both methylated.

What are housekeeping genes?

Genes that encode proteins required in most cells of an organism.

How are the CpG island in housekeeping genes methylated?

They are not methylated.

What are tissue-specific genes?

Genes that are highly regulated and only expressed in a particular cell type.

What role does DNA methylation play in tissue-specific genes?

They play an important role in the silencing of this genes, so that these genes are not being expressed in the wrong tissue.

Where must the methylation occur in order to have an effect on transcription, and why?

In the vicinity of the promoter, because methylated cytosines do not hinder the elongation phase of transcription.

What is an example of a protein that methyl-CpG-binding proteins recruit to the CpG island?

Histone deacetylase, which removes acetyl groups from the histone proteins, so that it is more difficult for nucleosomes to be removed from the DNA.

How is it possible that DNA methylation is heritable?

Following DNA replication, the pattern of methylation is retained.

How is DNA methylation inherited (steps)?

- The DNA in a cell becomes methylated by de novo methylation;
- After DNA replication, one strand of the newly made DNA is methylated and the other is not (hemimethylated);
- Those DNA strands are fully methylated by DNA methyltransferase (this process is called maintenance methylation).

To what extent are de novo methylation and demethylation regulated?

They are highly regulated.

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