Genome complexity: methylation control enzymes found (Introduction)

by David Turell , Monday, August 19, 2019, 18:32 (1712 days ago) @ David Turell

Studies in two bacteria show more complexity:

https://phys.org/news/2019-08-scientists-uncover-mystery-dna-methylation.html

"All species mark their DNA with methyl groups. This is done to regulate gene expression, distinguish indigenous DNA from foreign DNA, or to mark old DNA strands during replication. Methylation is carried out by certain enzymes called methyltransferases, which decorate DNA with methyl groups in certain patterns to create an epigenetic layer on top of DNA.

"Until now, scientists have not been struggling to tell which enzymes are responsible for which patterns. But in a new study, recently published in Nature Communications, scientists from The Novo Nordisk Foundation Center for Biosustainability (DTU Biosustain) at Technical University of Denmark have coupled enzymes with specific methylation patterns in two bacteria.

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"The goal was to find out, which enzymes are responsible for which patterns. In order to uncover this, the researchers constructed DNA-rings (plasmids) containing one of the methyltransferases and "cassettes" holding multiple copies of certain DNA patterns. These DNA-patterns, called motifs, are the targets for methyltransferases. By coupling the two, the methyltransferase expressed by the plasmid would mark the DNA in a specific way, thus, revealing the enzyme's methylation pattern.

"This was done for all methyltransferases. Afterwards, all the plasmids (in a pool) were read using a sequencing method designed to reveal methyl groups. This gave the researchers a "library" of enzyme-to-motif couplings.

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"This quick method of identifying methyltransferase methylation patterns holds great promise to other researchers struggling with DNA degradation, according to the research team.
To validate the method, the scientists analysed the genomes of the temperature resistant bacterium M. thermoacetica as well as the bacterium A. woodii. Both bacteria are hosts with great potential for industrial applications and substantially modified genomes.

"In total, the two bacterial organisms hold 23 methyltranstransferase genes, but only show modification on 12 different DNA-motifs on their genomes, meaning that not all methyltransferases are active.

"The team assessed all of the 23 methyltransferases, looking for those being active on the genomes. For 11 of the 12 motifs, they were able to couple activity to specific methyltransferases gene."

Comment: Epigenetic changes are controlled by specific enzymes. Not by chance.