WordNet

the 3rd letter of the Roman alphabet (同)c
(music) the keynote of the scale of C major
a general-purpose programing language closely associated with the UNIX operating system
a zone or area resembling an island
a land mass (smaller than a continent) that is surrounded by water

PrepTutorEJDIC

carbonの化学記号
『島』 / 島に似たもの;(街路上の)安全地帯(《米》safety island,《英》traffic island)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/10 17:53:29」(JST)

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cytosine

guanine

In genetics, CpG islands or CG islands are genomic regions that contain a high frequency of CpG sites. The "p" in CpG refers to the phosphodiester bond between the cytosine and the guanine, which indicates that the C and the G are next to each other in sequence, regardless of being single- or double- stranded. In a CpG site, both C and G are found on the same strand of DNA or RNA and are connected by a phosphodiester bond. This is a covalent bond between atoms, stable and permanent as opposed to the three hydrogen bonds established after base-pairing of C and G in opposite strands of DNA.

However, objective definitions for CpG islands are limited. The usual formal definition of a CpG island is a region with at least 200 bp, and a GC percentage that is greater than 50%, and with an observed-to-expected CpG ratio that is greater than 60%. The "observed-to-expected CpG ratio" is calculated by formula ((Num of CpG/(Num of C × Num of G)) × Total number of nucleotides in the sequence).^[1]

In mammalian genomes, CpG islands are typically 300-3,000 base pairs in length, and have been found in or near approximately 40% of promoters of mammalian genes.^[2] About 70% of human promoters have a high CpG content. Given the frequency of GC two-nucleotide sequences, the number of CpG dinucleotides is much lower than would be expected.^[3]

A 2002 study revised the rules of CpG island prediction to exclude other GC-rich genomic sequences such as Alu repeats. Based on an extensive search on the complete sequences of human chromosomes 21 and 22, DNA regions greater than 500 bp were found more likely to be the "true" CpG islands associated with the 5' regions of genes if they had a GC content greater than 55%, and an observed-to-expected CpG ratio of 65%.^[4]

CpG islands are characterized by CpG dinucleotide content of at least 60% of that which would be statistically expected (~4–6%), whereas the rest of the genome has much lower CpG frequency (~1%), a phenomenon called CG suppression. Unlike CpG sites in the coding region of a gene, in most instances the CpG sites in the CpG islands of promoters are unmethylated if the genes are expressed. This observation led to the speculation that methylation of CpG sites in the promoter of a gene may inhibit gene expression. Methylation is central to imprinting, along with histone modifications.^[5] Most of the methylation occurs a short distance from the CpG islands (at "CpG island shores") rather than in the islands themselves.^[6]

CpG islands typically occur at or near the transcription start site of genes, particularly housekeeping genes, in vertebrates.^[3] Normally a C (cytosine) base followed immediately by a G (guanine) base (a CpG) is rare in vertebrate DNA because the cytosines in such an arrangement tend to be methylated. This methylation helps distinguish the newly synthesized DNA strand from the parent strand, which aids in the final stages of DNA proofreading after duplication. However, over evolutionary time methylated cytosines tend to turn into thymines because of spontaneous deamination. While there is a special enzyme in human (Thymine-DNA glycosylase, or TDG) that specifically replaces T's from T/G mismatches, it is not sufficiently effective to prevent the relatively rapid mutation of the dinucleotides. The result is that CpGs are relatively rare. The existence of CpG islands is usually explained by the existence of selective forces for relatively high CpG content, or low levels of methylation in that genomic area, perhaps having to do with the regulation of gene expression. Recently a study showed that most CpG islands are a result of non-selective forces. ^[7]

References

^ Gardiner-Garden M, Frommer M (1987). "CpG islands in vertebrate genomes". Journal of Molecular Biology 196 (2): 261–82. doi:10.1016/0022-2836(87)90689-9. PMID 3656447.
^ Fatemi M, Pao MM, Jeong S, Gal-Yam EN, Egger G, Weisenberger DJ, Jones PA (2005). "Footprinting of mammalian promoters: use of a CpG DNA methyltransferase revealing nucleosome positions at a single molecule level". Nucleic Acids Res 33 (20): e176. doi:10.1093/nar/gni180. PMC 1292996. PMID 16314307. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1292996/.
^ ^a ^b Saxonov S, Berg P, Brutlag DL (2006). "A genome-wide analysis of CpG dinucleotides in the human genome distinguishes two distinct classes of promoters". Proc Natl Acad Sci USA 103 (5): 1412–1417. doi:10.1073/pnas.0510310103. PMC 1345710. PMID 16432200. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1345710/.
^ Takai D, Jones PA (2002). "Comprehensive analysis of CpG islands in human chromosomes 21 and 22.". Proc Natl Acad Sci USA 99 (6): 3740–5. doi:10.1073/pnas.052410099. PMC 122594. PMID 11891299. http://www.pnas.org/cgi/content/full/99/6/3740.
^ Feil R, Berger F (2007). "Convergent evolution of genomic imprinting in plants and mammals". Trends Genet 23 (4): 192–199. doi:10.1016/j.tig.2007.02.004. PMID 17316885.
^ Irizarry RA, Ladd-Acosta C, Wen B, Wu Z, Montano C, Onyango P, Cui H, Gabo K, Rongione M, Webster M, Ji H, Potash JB, Sabunciyan S, Feinberg AP (2009). "The human colon cancer methylome shows similar hypo- and hypermethylation at conserved tissue-specific CpG island shores". Nature Genetics 41 (2): 178-186. PMID 19151715. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2729128/.
^ Cohen N, Kenigsberg E, Tanay A (2011). "Primate CpG Islands Are Maintained by Heterogeneous Evolutionary Regimes Involving Minimal Selection". Cell 145 (5): 773–786. doi:10.1016/j.cell.2011.04.024. PMID 21620139.

External links

M. D. Anderson Cancer Center, mdanderson.org
CpG Island Searcher using the updated rules from Takai and Jones, cpgislands.usc.edu
EMBOSS CpGPlot/CpGReport/Isochore, ebi.ac.uk
Google Scholar Search for 'CpG Island', scholar.google.com.hk
CpG+Islands at the US National Library of Medicine Medical Subject Headings (MeSH)

UpToDate Contents

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English Journal

Epigenetic profiling of gallbladder cancer and gall stone diseases: Evaluation of role of tumour associated genes.

Singh TD1, Gupta S2, Shrivastav BR3, Tiwari PK4.
Gene.Gene.2016 Feb 1;576(2 Pt 2):743-52. doi: 10.1016/j.gene.2015.10.004. Epub 2015 Oct 8.
BACKGROUND: As on today, the global mortality rate of gallbladder cancer is still very high. Both genetic and epigenetic alterations play pivotal roles in the development of cancer. We selected seven tumour associated genes, implicated in other cancers, to assess their methylation status in gallblad
PMID 26456195

Epigenetic regulation of dorsal raphe GABAB1a associated with isolation-induced abnormal responses to social stimulation in mice.

Araki R1, Hiraki Y2, Nishida S2, Kuramoto N3, Matsumoto K4, Yabe T5.
Neuropharmacology.Neuropharmacology.2016 Feb;101:1-12. doi: 10.1016/j.neuropharm.2015.09.013. Epub 2015 Sep 11.
In isolation-reared mice, social encounter stimulation induces locomotor hyperactivity and activation of the dorsal raphe nucleus (DRN), suggesting that dysregulation of dorsal raphe function may be involved in abnormal behaviors. In this study, we examined the involvement of dorsal raphe GABAergic
PMID 26365570

Expression and DNA methylation alterations of seven cancer-associated 3p genes and their predicted regulator miRNAs (miR-129-2, miR-9-1) in breast and ovarian cancers.

Pronina IV1, Loginov VI1, Burdennyy AM1, Fridman MV1, Kazubskaya TP2, Dmitriev AA3, Braga EA4.
Gene.Gene.2016 Jan 15;576(1 Pt 3):483-91. doi: 10.1016/j.gene.2015.10.059. Epub 2015 Oct 28.
PMID 26519551

Japanese Journal

大腸鋸歯状病変群における表面微細構造別病理組織および遺伝子学的特徴 (特集大腸鋸歯状病変の内視鏡診断と治療)

木村友昭,山野泰穂,菅井有 [他]
消化器内科 55(2), 194-200, 2012-08
NAID 40019432906

DNA Methylation Profile : A Composer-, Conductor-, and Player-Orchestrated Mammalian Genome Consisting of Genes and Transposable Genetic Elements

YAGI Shintaro,HIROSAWA Mitsuko,SHIOTA Kunio
The Journal of reproduction and development 58(3), 265-273, 2012-06-01
… Epigenetic studies indicate that the molecules that perform these modifications directly, such as DNA methyltransferases and eukaryotic histone methyltransferases, or indirectly, such as CpG-binding protein and noncoding RNAs-and combinations of these-contribute to the DNA methylation profile. …
NAID 10030820772

Related Pictures

★リンクテーブル★

リンク元	「CpG島」
関連記事	「C」「island」

「CpG島」

　　[★]

英: CpG island
同: CG島 CG island

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CpG島 : 59 件
CG島 : 約 89 件

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CG island : 約 6,790 件

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CG island : 約 46 件

「C」

　　[★]

炭素 carbon
シトシン cytosine
システイン cysteine
シチジン
セルシウス度摂氏 degrees Celsius degree C
産婦人科領域で「子宮外頚子宮外頚部 exocervix」を表現するための略語

「island」

　　[★]

島、アイランド

関: county、geographic factor、geography

[Gardiner-Garden1987-1] Gardiner-Garden M, Frommer M (1987). "CpG islands in vertebrate genomes". Journal of Molecular Biology 196 (2): 261–82. doi:10.1016/0022-2836(87)90689-9. PMID 3656447.

[Fatemi2005-2] Fatemi M, Pao MM, Jeong S, Gal-Yam EN, Egger G, Weisenberger DJ, Jones PA (2005). "Footprinting of mammalian promoters: use of a CpG DNA methyltransferase revealing nucleosome positions at a single molecule level". Nucleic Acids Res 33 (20): e176. doi:10.1093/nar/gni180. PMC 1292996. PMID 16314307. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1292996/.

[Saxonov2006-3] Saxonov S, Berg P, Brutlag DL (2006). "A genome-wide analysis of CpG dinucleotides in the human genome distinguishes two distinct classes of promoters". Proc Natl Acad Sci USA 103 (5): 1412–1417. doi:10.1073/pnas.0510310103. PMC 1345710. PMID 16432200. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1345710/.

[Takai2002-4] Takai D, Jones PA (2002). "Comprehensive analysis of CpG islands in human chromosomes 21 and 22.". Proc Natl Acad Sci USA 99 (6): 3740–5. doi:10.1073/pnas.052410099. PMC 122594. PMID 11891299. http://www.pnas.org/cgi/content/full/99/6/3740.

[Feil2007-5] Feil R, Berger F (2007). "Convergent evolution of genomic imprinting in plants and mammals". Trends Genet 23 (4): 192–199. doi:10.1016/j.tig.2007.02.004. PMID 17316885.

[6] Irizarry RA, Ladd-Acosta C, Wen B, Wu Z, Montano C, Onyango P, Cui H, Gabo K, Rongione M, Webster M, Ji H, Potash JB, Sabunciyan S, Feinberg AP (2009). "The human colon cancer methylome shows similar hypo- and hypermethylation at conserved tissue-specific CpG island shores". Nature Genetics 41 (2): 178-186. PMID 19151715. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2729128/.

[Tanay2011-7] Cohen N, Kenigsberg E, Tanay A (2011). "Primate CpG Islands Are Maintained by Heterogeneous Evolutionary Regimes Involving Minimal Selection". Cell 145 (5): 773–786. doi:10.1016/j.cell.2011.04.024. PMID 21620139.

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案内

CpG island