Question

In mammalian cells, iMs have been shown be subject to two epigenetic modifications: methylation and hydroxymethylation. Which two classes of enzymes are needed in the two-step conversion of cytosine to 5hmC?

a) transferase and oxireductase
b) hydrolase and ligase
c) oxidoreductase and hydrolase
d) transferase and ligase

Answer 1

For the conversion of cytosine to 5hmC in mammalian cells, DNA methyltransferases and Tet proteins are needed to perform the methylation and subsequent hydroxymethylation of cytosine.

Step-by-step explanation:

The conversion of cytosine to 5-hydroxymethylcytosine (5hmC) involves a two-step enzymatic process. To answer the student's question, the two classes of enzymes needed are DNA methyltransferases, which add a methyl group to cytosine forming 5-methylcytosine (5mC), and then the enzymes known as Tet methylcytosine dioxygenases (Tet proteins) which convert 5mC to 5hmC through an oxidation reaction. Thereby, the correct answer among the given options is a) transferase (DNA methyltransferases) and oxidoreductase (Tet proteins).

DNA methylation patterns, regulated by DNA methyltransferases, are crucial for gene expression and are a part of epigenetic regulation. These patterns can be influenced by environmental factors and can sometimes be heritable, affecting the use of DNA for transcription. Similarly, various modifications of histones, such as in histone acetylation, methylation, and phosphorylation, are orchestrated by enzymes like histone acetyltransferases, methyltransferases, and kinases, which all play significant roles in chromatin remodeling and gene regulation.