Pathway: HDMs demethylate histones
Reactions in pathway: HDMs demethylate histones :
HDMs demethylate histones
Histone lysine demethylases (KDMs) are able to reverse N-methylations of histones and probably other proteins. To date KDMs have been demonstrated to catalyse demethylation of N-epsilon methylated lysine residues. Biochemically there are two distinct groups of N-epsilon methylated lysine demethylases with different catalytic mechanisms, both of which result in methyl group oxidation to produce formaldhyde. KDM1A, formerly known as Lysine Specific Demethylase 1 (LSD1), belongs to the flavin adenine dinucleotide (FAD)-dependent amino oxidase family. The KDM1A reaction mechanism requires a protonatable lysine epsilon-amine group, not available in trimethylated lysines, which consequently are not KDM1 substrates. Other KDMs belong to the Jumonji C (JmjC) -domain containing family. These are members of the Cupin superfamily of mononuclear Fe (II)-dependent oxygenases, which are characterised by the presence of a double-stranded beta-helix core fold. They require 2-oxoglutarate (2OG) and molecular oxygen as co-substrates, producing, in addition to formaldehyde, succinate and carbon dioxide. This hydroxylation-based mechanism does not require a protonatable lysine epsilon-amine group and consequently JmjC-containing demethylases are able to demethylate tri-, di- and monomethylated lysines.
The coordinates of post-translational modifications represented and described here follow UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed. Therefore the coordinates of post-translated residues in the Reactome database and described here are frequently +1 when compared with the literature.
In general, methylation at histone H3 lysine-5 (H3K4) and lysine-37 (H3K36), including di- and trimethylation at these sites, has been linked to actively transcribed genes (reviewed in Martin & Zhang 2005). In contrast, lysine-10 (H3K9) promoter methylation is considered a repressive mark for euchromatic genes and is also one of the landmark modifications associated with heterochromatin (Peters et al. 2002).
The first reported JmjC-containing demethylases were KDM2A/B (JHDM1A/B, FBXL11/10). These catalyse demethylation of histone H3 lysine-37 when mono- or di-methylated (H3K36Me1/2) (Tsukada et al. 2006). They were found to contain a JmjC catalytic domain, previously implicated in chromatin-dependent functions (Clissold & Ponting 2001). Subsequently, many other JmjC enzymes have been identified and discovered to have lysine demethylase activities with distinct methylation site and state specificities.
KDM3A/B (JHDM2A/B) are specific for mono or di-methylated lysine-10 on histone H3 (H3K9Me1/2) (Yamane et al. 2006, Kim et al. 2012). KDM4A-C (JMJD2A-C/JHDM3A-C) catalyse demethylation of di- or tri-methylated histone H3 at lysine-10 (H3K9Me2/3) (Cloos et al. 2006, Fodor et al. 2006), with a strong preference for Me3 (Whetstine et al. 2007). KDM4D (JMJD2D) also catalyses demethylation of H3K9Me2/3 (Whetstine et al. 2007). KDM4A-C (JHDM3A-C) can also catalyse demethylation of lysine-37 of histone H3 (H3K36Me2/3) (Klose et al. 2006). KDM5A-D (JARID1A-D) catalyses demethylation of di- or tri-methylated lysine-5 of histone H3 (H3K4Me2/3) (Christensen et al. 2007, Klose et al. 2007, Lee et al. 2007, Secombe et al. 2007, Seward et al. 2007, Iwase et al. 2007). KDM6A and KDM6B (UTX/JMJD3) catalyse demethylation of di- or tri-methylated lysine-28 of histone H3 (H3K27Me2/3) (Agger et al. 2007, Cho et al. 2007, De Santra et al. 2007, Lan et al. 2007, Lee et al. 2007).
KDM7A (KIAA1718/JHDM1D) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) and mono- and di-methylated lysine-28 of histone H3 (H3K27Me1/2) (Horton et al. 2010, Huang et al. 2010). PHF8 (JHDM1E) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) and mono-methylated lysine-21 of histone H4 (H4K20Me1) (Loenarz et al. 2010, Horton et al. 2010, Feng et al. 2010, Kleine-Kohlbrecher et al. 2010, Fortschegger et al. 2010, Qi et al. 2010, Liu et al. 2010). PHF2 (JHDM1E) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) (Wen et al, 2010, Baba et al. 2011). JMJD6 was initially characterized as an arginine demethylase that catalyses demethylation of mono or di methylated arginine 3 of histone H3 (H3R2Me1/2) and arginine 4 of histone H4 (H4R3Me1/2) (Chang et al. 2007) although it was subsequently also characterized as a lysine hydroxylase (Webby et al. 2009). N.B. The coordinates of post-translational modifications represented and described here follow UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed. Therefore the coordinates of post-translated residues in the Reactome database and described here are frequently +1 when compared with the literature.
The coordinates of post-translational modifications represented and described here follow UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed. Therefore the coordinates of post-translated residues in the Reactome database and described here are frequently +1 when compared with the literature.
In general, methylation at histone H3 lysine-5 (H3K4) and lysine-37 (H3K36), including di- and trimethylation at these sites, has been linked to actively transcribed genes (reviewed in Martin & Zhang 2005). In contrast, lysine-10 (H3K9) promoter methylation is considered a repressive mark for euchromatic genes and is also one of the landmark modifications associated with heterochromatin (Peters et al. 2002).
The first reported JmjC-containing demethylases were KDM2A/B (JHDM1A/B, FBXL11/10). These catalyse demethylation of histone H3 lysine-37 when mono- or di-methylated (H3K36Me1/2) (Tsukada et al. 2006). They were found to contain a JmjC catalytic domain, previously implicated in chromatin-dependent functions (Clissold & Ponting 2001). Subsequently, many other JmjC enzymes have been identified and discovered to have lysine demethylase activities with distinct methylation site and state specificities.
KDM3A/B (JHDM2A/B) are specific for mono or di-methylated lysine-10 on histone H3 (H3K9Me1/2) (Yamane et al. 2006, Kim et al. 2012). KDM4A-C (JMJD2A-C/JHDM3A-C) catalyse demethylation of di- or tri-methylated histone H3 at lysine-10 (H3K9Me2/3) (Cloos et al. 2006, Fodor et al. 2006), with a strong preference for Me3 (Whetstine et al. 2007). KDM4D (JMJD2D) also catalyses demethylation of H3K9Me2/3 (Whetstine et al. 2007). KDM4A-C (JHDM3A-C) can also catalyse demethylation of lysine-37 of histone H3 (H3K36Me2/3) (Klose et al. 2006). KDM5A-D (JARID1A-D) catalyses demethylation of di- or tri-methylated lysine-5 of histone H3 (H3K4Me2/3) (Christensen et al. 2007, Klose et al. 2007, Lee et al. 2007, Secombe et al. 2007, Seward et al. 2007, Iwase et al. 2007). KDM6A and KDM6B (UTX/JMJD3) catalyse demethylation of di- or tri-methylated lysine-28 of histone H3 (H3K27Me2/3) (Agger et al. 2007, Cho et al. 2007, De Santra et al. 2007, Lan et al. 2007, Lee et al. 2007).
KDM7A (KIAA1718/JHDM1D) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) and mono- and di-methylated lysine-28 of histone H3 (H3K27Me1/2) (Horton et al. 2010, Huang et al. 2010). PHF8 (JHDM1E) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) and mono-methylated lysine-21 of histone H4 (H4K20Me1) (Loenarz et al. 2010, Horton et al. 2010, Feng et al. 2010, Kleine-Kohlbrecher et al. 2010, Fortschegger et al. 2010, Qi et al. 2010, Liu et al. 2010). PHF2 (JHDM1E) catalyses demethylation of mono- or di-methylated lysine-10 of histone H3 (H3K9Me1/2) (Wen et al, 2010, Baba et al. 2011). JMJD6 was initially characterized as an arginine demethylase that catalyses demethylation of mono or di methylated arginine 3 of histone H3 (H3R2Me1/2) and arginine 4 of histone H4 (H4R3Me1/2) (Chang et al. 2007) although it was subsequently also characterized as a lysine hydroxylase (Webby et al. 2009). N.B. The coordinates of post-translational modifications represented and described here follow UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed. Therefore the coordinates of post-translated residues in the Reactome database and described here are frequently +1 when compared with the literature.
Eukaryotic DNA is associated with histone proteins and organized into a complex nucleoprotein structure called chromatin. This structure decreases the accessibility of DNA but also helps to protect it from damage. Access to DNA is achieved by highly regulated local chromatin decondensation.
The 'building block' of chromatin is the nucleosome. This contains ~150 bp of DNA wrapped around a histone octamer which consists of two each of the core histones H2A, H2B, H3 and H4 in a 1.65 left-handed superhelical turn (Luger et al. 1997, Andrews & Luger 2011).
Most organisms have multiple genes encoding the major histone proteins. The replication-dependent genes for the five histone proteins are clustered together in the genome in all metazoans. Human replication-dependent histones occur in a large cluster on chromosome 6 termed HIST1, a smaller cluster HIST2 on chromosome 1q21, and a third small cluster HIST3 on chromosome 1q42 (Marzluff et al. 2002). Histone genes are named systematically according to their cluster and location within the cluster.
The 'major' histone genes are expressed primarily during the S phase of the cell cycle and code for the bulk of cellular histones. Histone variants are usually present as single-copy genes that are not restricted in their expression to S phase, contain introns and are often polyadenylated (Old & Woodland 1984). Some variants have significant differences in primary sequence and distinct biophysical characteristics that are thought to alter the properties of nucleosomes. Others localize to specific regions of the genome. Some variants can exchange with pre-existing major histones during development and differentiation, referred to as replacement histones (Kamakaka & Biggins 2005). These variants can become the predominant species in differentiated cells (Pina & Suau 1987, Wunsch et al. 1991). Histone variants may have specialized functions in regulating chromatin dynamics.
The H2A histone family has the highest sequence divergence and largest number of variants. H2A.Z and H2A.XH2A are considered 'universal variants', found in almost all organisms (Talbert & Henikoff 2010). Variants differ mostly in the C-terminus, including the docking domain, implicated in interactions with the (H3-H4)x2 tetramer within the nucleosome, and in the L1 loop, which is the interaction interface of H2A-H2B dimers (Bonisch & Hake 2012). Canonical H2A proteins are expressed almost exclusively during S-phase. There are several nearly identical variants (Marzluff et al. 2002). No functional specialization of these canonical H2A isoforms has been demonstrated (Bonisch & Hake 2012). Reversible histone modifications such as acetylation and methylation regulate transcription from genomic DNA, defining the 'readability' of genes in specific tissues (Kouzarides 2007, Marmorstein & Trievel 2009, Butler et al. 2012).
N.B. The coordinates of post-translational modifications represented here follow Reactome standardized naming, which includes the UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed; therefore the coordinates of post-translated histone residues described here are frequently +1 when compared with the literature. For more information on Reactome's standards for naming pathway events, the molecules that participate in them and representation of post-translational modifications, please refer to Naming Conventions on the Reactome Wiki or Jupe et al. 2014.
The 'building block' of chromatin is the nucleosome. This contains ~150 bp of DNA wrapped around a histone octamer which consists of two each of the core histones H2A, H2B, H3 and H4 in a 1.65 left-handed superhelical turn (Luger et al. 1997, Andrews & Luger 2011).
Most organisms have multiple genes encoding the major histone proteins. The replication-dependent genes for the five histone proteins are clustered together in the genome in all metazoans. Human replication-dependent histones occur in a large cluster on chromosome 6 termed HIST1, a smaller cluster HIST2 on chromosome 1q21, and a third small cluster HIST3 on chromosome 1q42 (Marzluff et al. 2002). Histone genes are named systematically according to their cluster and location within the cluster.
The 'major' histone genes are expressed primarily during the S phase of the cell cycle and code for the bulk of cellular histones. Histone variants are usually present as single-copy genes that are not restricted in their expression to S phase, contain introns and are often polyadenylated (Old & Woodland 1984). Some variants have significant differences in primary sequence and distinct biophysical characteristics that are thought to alter the properties of nucleosomes. Others localize to specific regions of the genome. Some variants can exchange with pre-existing major histones during development and differentiation, referred to as replacement histones (Kamakaka & Biggins 2005). These variants can become the predominant species in differentiated cells (Pina & Suau 1987, Wunsch et al. 1991). Histone variants may have specialized functions in regulating chromatin dynamics.
The H2A histone family has the highest sequence divergence and largest number of variants. H2A.Z and H2A.XH2A are considered 'universal variants', found in almost all organisms (Talbert & Henikoff 2010). Variants differ mostly in the C-terminus, including the docking domain, implicated in interactions with the (H3-H4)x2 tetramer within the nucleosome, and in the L1 loop, which is the interaction interface of H2A-H2B dimers (Bonisch & Hake 2012). Canonical H2A proteins are expressed almost exclusively during S-phase. There are several nearly identical variants (Marzluff et al. 2002). No functional specialization of these canonical H2A isoforms has been demonstrated (Bonisch & Hake 2012). Reversible histone modifications such as acetylation and methylation regulate transcription from genomic DNA, defining the 'readability' of genes in specific tissues (Kouzarides 2007, Marmorstein & Trievel 2009, Butler et al. 2012).
N.B. The coordinates of post-translational modifications represented here follow Reactome standardized naming, which includes the UniProt standard practice whereby coordinates refer to the translated protein before any further processing. Histone literature typically refers to coordinates of the protein after the initiating methionine has been removed; therefore the coordinates of post-translated histone residues described here are frequently +1 when compared with the literature. For more information on Reactome's standards for naming pathway events, the molecules that participate in them and representation of post-translational modifications, please refer to Naming Conventions on the Reactome Wiki or Jupe et al. 2014.
Chromatin organization refers to the composition and conformation of complexes between DNA, protein and RNA. It is determined by processes that result in the specification, formation or maintenance of the physical structure of eukaryotic chromatin. These processes include histone modification, DNA modification, and transcription. The modifications are bound by specific proteins that alter the conformation of chromatin.