During apoptosis, H3T45 phosphorylation is required for structural changes inside the nucleosome that enable DNA nicking and/or fragmentation.
The H3T45 residue appears to be a nucleosome gatekeeper, regulating DNA accessibility at transcription target sites.
[2] H3T45 is phosphorylated by a histone kinase complex that includes the conserved S-phase replication start enzyme Cdc7, its activating protein Dbf4, and a number of other components.
[3] The H3T45 residue appears to be a nucleosome gatekeeper, regulating DNA accessibility at transcription target sites.
Researchers choose proteins that are known to modify histones to test their effects on transcription, and found that the stress-induced kinase, MSK1, inhibits RNA synthesis.
Thus results suggested that the acetylation of histones can stimulate transcription by suppressing an inhibitory phosphorylation by a kinase as MSK1.
Because of the ease with which proteins can be phosphorylated and dephosphorylated, this type of modification is a flexible mechanism for cells to respond to external signals and environmental conditions.
Reversible phosphorylation results in a conformational change in the structure in many enzymes and receptors, causing them to become activated or deactivated.
[10] In prokaryotic proteins phosphorylation occurs on the serine, threonine, tyrosine, histidine or arginine or lysine residues.
[12] The current understanding and interpretation of histones comes from two large scale projects: ENCODE and the Epigenomic roadmap.
This led to chromatin states, which define genomic regions by grouping different proteins and/or histone modifications together.
[15] A look in to the data obtained led to the definition of chromatin states based on histone modifications.