Heterochromatin: Constitutive

Abstract

Heterochromatin consists of a variety of nontranscribed tandemly repeated and interspersed repetitive deoxyribonucleic acid DNA sequences. The major classes of tandemly repeated DNA are: satellite DNA, composed of very long arrays mainly found in and around centromeres; minisatellite DNA, composed of moderately sized arrays located at or close to telomeres; and microsatellites, defined by short arrays and dispersed throughout the human genome. long interspersed nuclear elements and short interspersed nuclear elements are the two major classes of interspersed repeats, also referred to as transposon‐derived repeats. Rare fragile sites involve large expansions of microsatellites or minisatellites.

Keywords: heterochromatin; satellite DNA; LINEs, SINEs; minisatellites; centromere‐associated proteins; fragile sites

Figure 1.

Half karyotypes from metaphases showing the CBG bands (C bands by barium hydroxide using Giemsa) (left) and the double distamycin A/4,6‐diamino‐2‐phenol‐indole (DA/DAPI) staining (right).

Figure 2.

Location of different classes of satellite DNA (indicated by differently shaded regions) at the centromeric and pericentromeric regions of the idiogrammed chromosomes 1, 9, 14, 16 and Y. The arrowed black square brackets to the left of each chromosome indicate the major sites of methylcytosine‐rich heterochromatin.

Figure 3.

General distribution of interspersed LINE‐1 and SINE‐Alu sequences (black arrows) and tandemly repeated DNA (differently shaded regions) on an idealized chromosome. The arrowed black square brackets to the left indicate the sites of methylcytosine‐rich heterochromatin corresponding to T bands.

Figure 4.

Hybridization of conserved alphoid (p82H) and telomeric sequences in the centromeric and telomeric regions of metaphase chromosomes. The probes (bright spots) are detected using fluoresceinisothiocyanate (FITC). The chromosomes are counterstained with 4,6‐diamino‐2‐phenol‐indole (DAPI).

Figure 5.

Partial QFQ‐banded metaphases showing chromosome breaks at the expressed rare folate‐sensitive fragile site fra(10)(q23.3) or fra(10)(q24.2) (FRA10A) (a) and the common aphidicolin inducible fragile site, fra(7)(q36) (FRA7I) (b).

close

References

Choo KHA (2000) Centromerization. Trends in Cell Biology 10: 182–188.

Greig G and Willard H (1992) β Satellite DNA: characterization and localization of two subfamilies from the distal and proximal short arms of the human acrocentric chromosomes. Genomics 12: 573–580.

Guy J, Spalluto C, McMurray A, et al. (2000) Genomic sequence and transcriptional profile of the boundary between pericentromeric satellites and genes on human chromosome arm 10q. Human Molecular Genetics 9: 2029–2042.

Korenberg JR and Rykowski MC (1988) Human genome organization: Alu, Lines, and the molecular structure of metaphase chromosome bands. Cell 53: 391–400.

Lee C, Wevrick R, Fisher RB, Ferguson‐Smith MA and Lin CC (1997) Human centromeric DNAs. Human Genetics 100: 291–304.

Moyzis RK, Buckingham JM, Cram LS, et al. (1988) A highly conserved repetitive DNA sequence (TTAGGG)n at the telomeres of human chromosomes. Proceedings of the National Academy of Sciences of the United States of America 85: 6622–6626.

Murphy TD and Karpen GH (1998) Centromeres take flight: alpha satellite and the quest for the human centromere. Cell 93: 317–320.

Nadir E, Margalit H, Gallily T and Ben‐Sasson SA (1996) Microsatellite spreading in the human genome: evolutionary mechanisms and structural implications. Proceedings of the National Academy of Sciences of the United States of America 93: 6470–6475.

Pidoux AL and Allshire RC (2000) Centromeres: getting a grip of chromosomes. Current Opinion in Cell Biology 12: 308–319.

Royle NJ, Clarkson RE, Wong Z and Jeffreys AJ (1988) Clustering of hypervariable minisatellites in the proterminal regions of human autosomes. Genomics 3: 352–360.

Sutherland GR, Baker E and Richards RI (1998) Fragile sites still breaking. Trends in Genetics 14: 501–506.

Verma RS (1980) Human chromosomal heteromorphisms: nature and clinical significance. International Review of Cytology 62: 361–433.

Warburton PE (2001) Epigenetic analysis of kinetochore assembly on variant human centromeres. Trends in Genetics 17: 243–247.

Further Reading

Ballif BC, Kashork CD and Shafer LG (2000) The promise and pitfalls of telomere region‐specific probes. American Journal of Human Genetics 67: 1356–1359.

Barbin A, Montpellier C, Kokalj‐Vokac N, et al. (1994) New sites of methylcytosine‐rich DNA detected on metaphase chromosomes. Human Genetics 94: 684–692.

Brown WRA, MacKinnon, Villasanté A, et al. (1990) Structure and polymorphism of human‐telomere‐associated DNA. Cell 63: 119–132.

Haaf T and Schmid M (2000) Experimental condensation inhibition in constitutive and facultative heterochromatin of mammalian chromosomes. Cytogenetics and Cell Genetics 91: 113–123.

Henikoff S (2000) Heterochromatin function in complex genomes. Biochimica Biophysica Acta 1470: 1–8.

Hennig W (1999) Heterochromatin. Chromosoma 108: 1–9.

Schlotterer C (2000) Evolutionary dynamics of microsatellite DNA. Chromosoma 109: 365–371.

Smit A (1999) Interspersed repeat and other mementos of transposable elements in mammalian genomes. Current Opinion in Genetics and Development 9: 657–663.

Sutherland GR and Richards RI (1999) Fragile sites – cytogenetic similarity with molecular diversity. American Journal of Human Genetics 64: 354–359.

The BAC Resorce Consortium (2001) Integration of cytogenetic landmarks into the draft sequence of the human genome. Nature 409: 953–958.

Web Links

Caveolin 1, caveolae protein, 22 kDa (CAV1); Locus ID: 857. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=857

Caveolin 2 (CAV2); Locus ID: 858. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=858

Fragile site, aphidicolin type, common, fra(3)(p14.2) (FRA3B); Locus ID: 2385. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=2385

Fragile site, aphidicolin type, common, fra(7)(q31.2) (FRA7G); Locus ID: 2414. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=2414

WW domain containing oxidoreductase (WWOX); Locus ID: 51741. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=51741

Caveolin 1, caveolae protein, 22 kDa (CAV1); MIM number: 601047. OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?601047

Caveolin 2 (CAV2); MIM number: 601048. OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?601048

Fragile site, aphidicolin type, common, fra(3)(p14.2) (FRA3B); MIM number: 601153. OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?601153

Fragile site, aphidicolin type, common, fra(7)(q31.2) (FRA7G); MIM number: 606085. OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?606085

WW domain containing oxidoreductase (WWOX); MIM number: 605131. OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?605131

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Larizza, Lidia, and Doneda, Luisa(Jan 2006) Heterochromatin: Constitutive. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0005786]