The circuit consists of a kinase and phosphatase acting on multiple sites of a substrate that, contingent on its modification state, catalyzes its own phosphorylation and, in a symmetric scenario, dephosphorylation.
As the specific activity of p53 is regulated at a post-translational level by sets of enzymes that mediate phosphorylation, acetylation, methylation, and ubiquitin-like modifications, it is likely that physiological modifiers of the aging function of p53 would be enzymes that catalyze such covalent modifications.
PRC2 is a critical regulator of histone modification, which catalyzes the trimethylation of H3K27 to mediate gene silencing.
The H3K27me3 modification is catalyzed by PRC2, and it is known that PRC1 and PRC2 do not occupy completely identical sets of genes within a given cell type [ 28, 35].
It is recognized that histone modification is catalyzed by several enzymes which modulate the histone markers.
This modification is catalyzed by the histone methyltransferase Su var)3-9 [ 11] and it is recognized and bound by heterochromatin protein 1 (HP1) [ 12].
This modification is catalyzed by Clr4, a homolog of the mammalian histone methyltransferase, SUV39H1 (Nakayama et al., 2001b).
The required modification is catalyzed by the ubiquitinating complex, LUBAC; the RLR-activated IRF3 is recruited to LUBAC via TRAF2- and TRAF6-dependent mechanism.
Work over the past several years has unraveled details for how the various DNA glycosylases survey DNA, detect damage within the duplex, select for the correct modification, and catalyze base excision.
This modification is catalyzed by a family of evolutionarily conserved enzymes called protein arginine methyltransferases (PRMTs).
