RR7: Chromatin and Epigenetics: The Histone Code

histone

core of nucleosome, which is associated w/ DNA, has + internal tails and binds to - DNA phosphate backbone

heterochromatin

transcriptionally inactive condensed form of chromatin that localizes at the nuclear envelope often near the nuclear pores, maintains in heterochromatic state

euchromatin

delicate, thread like form of chromatin abundant in actively transcribing cels, w/ less e- density

epigenetic trait

trait transmitted independently of the DNA sequence itself due to imprints of methylation or acetylation

epigenetic writer

histone mark that can nucleate histone methyltransferases to repress gene activity across an entire genetic region, heritable following cell divisions

epigenetic reader

protein that recognizes histone mark modifications

pioneer transcription factor

DNA binding transcriptional activators that function by interacting w/ DNA via sequences exposed on the outside of the DNA wound histone octamer that recruits enzymes that alter the configuration of neighboring histone tails, which opens chromatin and permits association w/ general transcription factors

histone H3 lysine 9 methyl transferase

enzyme that methylates histone lysine 9 on newly synthesiez histone octamers assembled on the daughter DNA

polycomb

essential repressor protein for maintaining the repression of genes in specific cell types and the cells that descend from them, through the life of an organism

PRC1

protein binding nucleosomes w/ H3K37me2 & 3 through himeric Pc subunits, which each contain methyl lysine binding chromodomain specific for methylated H3 lysine 27, condensing chromatin into structure that inhibits transcription and contains ubiquitin ligase that monounbiquitinate histone H2A at lysine 119 in the H2A of the C terminal tail

PRC2

protein w/ histone deacetylases that inhibit transcription and a subunit w/ a SET domain

SET domain

catalytic domain of several histone methyltransferases, which methylates H3 on lysine 27, generating tri/dimethyl lysines (H3K27me2&3), part of PRC2

long noncoding RNA

ribonucleic acid lacking open reading grames, which can repress genes on the the same chromosomes in which the DNA is transcribed

X inactivation center

region that encodes several lncRNAs required for random inactivation of one X chromsome in females