In bacteria, an enzyme called dam methylase (Deoxyadenosine methylase) methylates adenines (A) in the sequence GATC in the new strand formed after replication. What role does this methylation play? I read that it has something to do with proofreading. If this is so, then how?
The dam methylase has three different functions:
- Correction replication errors, since the new DNA molecule is only hemimethylated (the old strand is methylated, the newly synthesized is not). Since the proof-reading only takes place on the new strand, errors introduced during replication can be corrected.
- Regulation of replication: The ori of the chromosome is methylated to ensure that is only replicated once.
- Regulation of transcription: Methylation of GATC sequences promote the transcription of genes.
For further details see the references.