three degrees of methylation
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Ohayou
Gozaimasu
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MethylationThree degrees of
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Specific HMTs differentially methylateH3 Lys9 to a certain degree.
Monomethylation
Dimethylation
Trimethylation
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-amino group of lysine can accept up to
three methyl groups and hence can be
mono-, di- or trimethylated
Rice JC, Allis CD: Histone methylation versus histone
acetylation: new insights into epigenetic regulation.
Curr Opin Cell Biol 2001, 13:263-273.
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Zhang K, Tang H, Huang L, Blankenship JW, Jones PR, Xiang F, Yau
PM, Burlingame AL: Anal Biochem 2002, 306:259-269.
Zhang L, Eugeni EE, Parthun MR, Freitas MA: Chromosoma 2003,
112:77-86Cocklin RR, Wang M: J Protein Chem 2003, 22:327-334
etric techniquesidentified several human his
includingo-, di- or trimethylated in vivo
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Recent reports indicate that these
different degrees of methylation are
correlated with different degrees of
gene regulation.Santos-Rosa H, Schneider R, Bannister AJ, Sherriff J, Bernstein BE,
Emre NC, Schreiber SL, Mellor J, Kouzarides T:Nature 2002, 419:407-411.
Ex. the conversion of dimethyl to trimethyl
histone H3 lysine 4 at gene promoters by the
budding yeast HMT, Set1, was exclusively
associated with actively transcribed genes
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port demonstrates that recombinant
urine HMT, dimethylates H3 Lys9 in
Yang L, Xia L, Wu DY, Wang H, Chansky HA, Schubach WH,
Hickstein DD, Zhang Y:Oncogene 2002, 21:148-152
Wang H, An W, Cao R, Xia L, Erdjument-Bromage H, Chatton B,
Tempst P, Roeder RG, Zhang Y:Mol Cell 2003, 12:475-487
These in vitro findings are consistent with recent in vivo
findings.
AM complex facilitates the
on of dimethyl to trimethyl H3 Lys9
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Rice JC, Briggs SD, Ueberheide B, Barber CM, Shabanowitz J,
Hunt DF, Shinkai Y, Allis CD: Mol Cell 2003, 12:1591-1598.
Peters AH, Kubicek S, Mechtler K, OSullivan RJ, Derijck AA,
Perez-Burgos L, Kohlmaier A, Opravil S, Tachibana M, Shinkai Y
et al: Mol Cell 2003,12:1577-1589.
In contrast to the localization of
H3 Lys9 trimethylation to
constitutive heterochromatin,
H3 Lys9 mono- and
dimethylation were found to be
enriched within transcriptionally
silent regions in the
chromosomal arms.
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The G9a HMT was found to be responsible
for the vast majority of H3 Lys9dimethylation and most monomethylation
in mouse embryonic stem cells.
Lack of G9a resulted in a global increase in histone
modifications associated with transcription
Tachibana M, Sugimoto K, Nozaki M, Ueda J, Ohta T, Ohki M,
Fukuda M, Takeda N, Niida H, Kato H et al: Genes Dev 2002, 16:1779-1791.
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The major targets of heterochromatin
formation, however, are DNA repetitive
elements such as transposons and thesatellite repeats associated with
centromeres and telomeres
Hall IM, Grewal SIS: Structure and function of heterochromatin:
Cold Spring Habor Laboratory Press; 2003:205-23
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In fission yeast, the dg and dh repeats (alsoknown as K repeats), which are associated with
centromeres, telomeres and the silent mating-
type region, are potent modulators of
heterochromatin formation.
Increasing evidence indicates, that the repetitive
nature of these DNA elements is a key factor
Hall IM, Grewal SIS: Structure and function of heterochromatin:
Cold Spring Habor Laboratory Press; 2003:205-232.
Selker EU: Repeat-induced gene silencing in fungi. Adv Genet
2002, 46:439-450.
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Also in fission yeast, the deletion of a
DNA element (cenH), which shares
homology to centromeric repeats,
resulted in
Grewal SI, Klar AJ: Genetics 1997, 146:1221-1238.
defects in heterochromatin
assembly throughout a 20-kilobasechromosomal domainof the mating-type region.
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In contrast to the involvement of
centromeric repeats in heterochromatin
assembly, the transgene-induced silencingreported in plants and, to a lesser degree, in
Drosophilahas not yet been observed in
fission yeast.
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