Human PAD4 Regulates Histone Arginine Methylation Levels via Demethylimination: SUMMARY

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Histone proteins bind to the long DNA molecules and help compacts them into the euakryotic cell nucleus. Enzymes that covalently modify histone come in pairs that have opposing effects on gene regulation. For example acetylases and deactylases or kinases and phosphatases. Among these enzymes are the arginine methyltransferases and lysine methyltransferases that add methyl groups to these two amino acid residues of histones during gene regulation.
Unlike the the other enzymes mentioned above that work in opposite to each other that requires one to catalyze the addition of reactive groups and the other to remove the reactive groups; in this article, these athors describe a new enzyme (human pepetidylarginine deiminase 4 (HumanPAD4) that can perform two functions:
1. It can convert the undmodified arginine residue to citrulline in histone
2. It can also convert the methylated arginine residues in histone to citrulline by "demethyliminating" (i.e removal of the methyl group).
The significance of this is that PAD4 can modulate the expression of genes that are regulated by arginine methylases. This enzyme is thought to be the first histone demethylase enzyme identified.

Nason Pue