Increased activity of CDK1:CCNB1 during the cell cycle promotes PHF8 dissociation from chromatin, while the inhibition of CDK activity promotes binding of PHF8 to chromatin during mitosis. CDK1:CCNB1 complex phosphorylates PHF8 in vitro on serine residues S33 and S84. Mutation of PHF8 phosphorylation sites impairs the dissociation of PHF8 from chromatin and the accumulation of H4K20me1 in prophase (Liu et al. 2010). Positions of CDK1-phosphorylated serine residues in PHF8, S33 and S84, are based on the sequence of PHF8 splicing isoform 2, which was used in the experiments of Liu et al. In PHF8 splicing isoforms 1 and 3, serine residues S69 and S120 are annotated as targets of CDK1-mediated phosphorylation.

PHF8, a PHD and Jumonji C domain-containing protein, is recruited to chromatin by binding to dimethylated or trimethylated histone H3 - H3K4me2 and/or H3K4me3. PHF8 demethylates monomethylated histone H4, H4K20me1, a docking site for the condesin II complex (Liu et al. 2010).

PHF8 (JHDM1E) catalyses demethylation of mono-methylated lysine-21 of histone H4 (H4K20Me1) (Qi et al. 2010, Liu et al. 2010).

All characterized lysine demethylases other than KDM1A belong to the jumonjiC domain (JmjC) containing family.The JmjC KDMs are members of the Cupin superfamily of mononuclear Fe (II) dependent oxygenases, which are characterized by the presence of a double-stranded beta-helix core fold. The JmjC KDMs require 2 oxoglutarate (2 OG) and molecular oxygen as co substrates, producing, along with 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 catalyse demethylateion of tri , di and monomethylated lysines. KDM3A (JHDM2A), KDM3B (JHDM2B), KDM7A (JHDM1D), PHF8 (JHDM1E) and PHF2 when complexed with ARID5B (Wen et al. 2010, Baba et al. 2011) are specific for mono or di-methylated lysine-10 on histone H3 (H3K9Me1/2) (Yamane et al. 2006, Kim et al. 2012, Horton et al. 2010, Huang et al. 2010, Loenarz et al. 2008, Feng et al. 2010, Fortschegger et al. 2010, Qi et al. 2010).

All characterized lysine demethylases other than KDM1A belong to the jumonjiC domain (JmjC) containing family.The JmjC KDMs are members of the Cupin superfamily of mononuclear Fe (II) dependent oxygenases, which are characterized by the presence of a double-stranded beta-helix core fold. The JmjC KDMs require 2 oxoglutarate (2 OG) and molecular oxygen as co substrates, producing, along with 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 catalyse demethylateion of tri , di and monomethylated lysines. KDM3A (JHDM2A), KDM3B (JHDM2B), KDM7A (JHDM1D), PHF8 (JHDM1E) and PHF2 when complexed with ARID5B (Wen et al. 2010, Baba et al. 2011) are specific for mono or di-methylated lysine-10 on histone H3 (H3K9Me1/2) (Yamane et al. 2006, Kim et al. 2012, Horton et al. 2010, Huang et al. 2010, Loenarz et al. 2008, Feng et al. 2010, Fortschegger et al. 2010, Qi et al. 2010).

Accumulation of monomethylated histone H4 (H4K20me1) is necessary for loading of the condensin II complex on chromatin. Condensin II binds H4K20me1 through HEAT repeats of two condensin II subunits, NCAPD3 and NCAPG2 (Liu et al. 2010). RB1 is required, at least partially, for the successful association of condensin II with chromatin (Longworth et al. 2008). The precise role of RB1 in condensin II loading and the connection, if any, between histone H4 monomethylation and RB1-facilitated loading of the condensin II complex on chromatin has not, however, been elucidated. RB1 family proteins are known to interact with H4K20 trimethylating enzymes Suv4-20h1 and Suv4-20h2 and promote H4K20 trimethylation at pericentric and telomeric heterochromatin (Gonzalo et al. 2005).

In mitotic prophase, the action of the condensin II complex enables initial chromosome condensation.

The condensin II complex subunit NCAPD3 binds monomethylated histone H4 (H4K20me1), thereby associating with chromatin (Liu et al. 2010). Binding of the condensin II complex to chromatin is partially controlled by the presence of RB1 (Longworth et al. 2008).

Two mechanisms contribute to the accumulation of H4K20me1 at mitotic entry. First, the activity of SETD8 histone methyltransferase peaks at G2/M transition (Nishioka et al. 2002, Rice et al. 2002, Wu et al. 2010). Second, the complex of CDK1 and cyclin B1 (CDK1:CCNB1) phosphorylates PHF8 histone demethylase at the start of mitosis, removing it from chromatin (Liu et al. 2010).

Condensin II complex needs to be phosphorylated by the CDK1:CCNB1 complex, and then phosphorylated by PLK1, in order to efficiently condense prophase chromosomes (Abe et al. 2011).

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.