The key difference between de novo methylation and maintenance methylation is that de novo methylation utilizes the enzymes DNMT3A and DNMT3B, while maintenance methylation utilizes one enzyme, DNMT1.
DNA methylation is a process essential for transcriptional regulation, silencing of transposable elements, and genome stabilization. De novo methylation and maintenance methylation are two key components of the cellular DNA methylation process that maintain the proper functioning of the cellular DNA replication process.
CONTENTS
1. Overview and Key Difference
2. What is De Novo Methylation
3. What is Maintenance Methylation
4. Similarities – De Novo Methylation and Maintenance Methylation
5. De Novo Methylation vs Maintenance Methylation in Tabular Form
6. Summary – De Novo Methylation vs Maintenance Methylation
What is De Novo Methylation?
De novo methylation is a process by which the addition of methyl groups to unmethylated DNA takes place at specific CpG sites. Normally CpG sites are unmethylated and DNA methylation occurs in these sites frequently. CpG sites are the specific regions of DNA in which cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5′ → 3′ direction. De novo methylation is catalyzed by two different methylates: DNMT3A and DNMT3B. Due to the precise maintenance of DNA methylation patterns in most differentiated cells, de novo DNA methylation is undesirable
Figure 01:De novo methylation
This process takes place in the entire population of male germ cells around the time of birth, and the pattern of methylation will exist until the end of the reproductive cycle. This should be propagated with the maintenance methylation process in spermatogonia. The important role of de novo methylation is that it compartmentalizes the genome during tissue differentiation, which results in the establishment of tissue-specific gene expression patterns.
What is Maintenance Methylation?
Maintenance methylation is an activity that is necessary to preserve DNA methylation after every cellular DNA replication cycle. DNA nucleotide methyl transferase 1 mediates the methylation pattern of DNA during replication.
Figure 02: Maintenance Methylation
DNMT1 methylates newly synthesized CpG sequences depending on the methylation status of the template strand. Here, UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1), which is a bridging protein, interacts with DNMT1 and hemimethylated CpG. This will lead to the maintenance of hemimethylated CpG dinucleotides pattern at the DNA fork. Without DNA nucleotide methyl transferase 1, the machinery of replication will produce daughter strands that are unmethylated. This, in the end, would lead to passive demethylation. Therefore, maintenance methylation is an important process responsible for copying DNA methylation patterns to the daughter strands during DNA replication.
What are the Similarities Between De Novo Methylation and Maintenance Methylation?
- De novo methylation and maintenance methylation are cellular processes.
- Moreover, they involve in DNA replication.
- Both are key components of the DNA methylation process.
- These processes consist of different catalysts.
- Both de novo methylation and maintenance methylation are important irreplaceable processes during DNA replication.
What is the Difference Between De Novo Methylation and Maintenance Methylation?
De novo methylation utilizes the enzymes DNMT3A and DNMT3B, while maintenance methylation utilizes one enzyme, DNMT1. Thus, this is the key difference between de novo methylation and maintenance methylation. The catalyst UHRF1 is not used in de novo methylation, whereas it is used in maintenance methylation. Moreover, failure in de novo methylation leads to epigenetic effects, while failure in maintenance methylation leads to passive methylation.
The below infographic presents the differences between de novo methylation and maintenance methylation in tabular form for side-by-side comparison.
Summary – De Novo Methylation vs Maintenance Methylation
DNA methylation is essential for transcriptional regulation, silencing of transposable elements, and genome stabilization. De novo methylation and maintenance methylation are two key components of the cellular DNA methylation process. De novo methylation utilizes the enzymes DNMT3A and DNMT3B, while maintenance methylation utilizes one enzyme, DNMT1. De novo methylation compartmentalizes the genome during tissue differentiation, which results in the establishment of tissue-specific gene expression patterns. Maintenance methylation is responsible for copying DNA methylation patterns to the daughter strands during DNA replication. So, this summarizes the difference between De novo methylation and maintenance methylation.
Reference:
1. Motoko, Unoki. “Recent Insights into the Mechanisms of De Novo and Maintenance of DNA Methylation in Mammals.” Research Gate.
2. G; Moore LD; LeT; Fan. “DNA Methylation and Its Basic Function.” Neuropsychopharmacology : Official Publication of the American College of Neuropsychopharmacology, U.S. National Library of Medicine.
Image Courtesy:
1. “DNA methylation” By Mariuswalter – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “DNAme landscape” By Mariuswalter – Own work (CC BY-SA 4.0) via Commons Wikimedia