Unusual molecular characteristics of a repeat sequence island within a Giemsa-positive band on the mouse X chromosome.

Nasir, Jamal; Fisher, Elizabeth; Brockdorff, Neil; Disteche, Christine M.; Lyon, Mary F.; Brown, S. D. M.

doi:10.1073/pnas.87.1.399

Cited by 27 publications

(14 citation statements)

References 27 publications

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“…This result is consistent with previously published cytogenetic and immunoprecipitation analyses (22,36). The DXSmh141 probe, corresponding to a long complex repeat unit sequence island located in the Giemsa-positive A3 band on the mouse X chromosome (28,37), also hybridizes predominantly to the antibody unbound (hypoacetylated) chromatin fraction. This observation concurs with cytogenetic analysis of histone H4 acetylation levels that suggest that late-replicating Giemsanegative bands are hypoacetylated (36).…”

Section: Resultssupporting

confidence: 81%

Chromatin structure analysis of the mouse Xist locus

McCabe

Formstone²,

O’Neill³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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The Xist gene is expressed exclusively from the inactive X chromosome and plays a central role in regulating X chromosome inactivation. Here we describe experiments aimed at defining the extent of the active chromatin domain of the expressed Xist allele. By using an allelespecific general DNaseI sensitivity assay we show that there is preferential digestion of the expressed allele at sites within the transcribed locus but not in f lanking sites located up to 70 kb 5. A putative proximal boundary for the Xist domain is located within 10 kb upstream of promoter P 1 . Chromatin in the expressed domain was found to be acetylated at H4 in XX somatic cells but also in XY cells, where Xist is never expressed. A single clear exception to this was the Xist promoter, which is acetylated only in XX cells. These observations concur with the view that H4 acetylation may not be a general marker of active chromatin domains and further support data implicating local promoter acetylation as being of primary functional significance in vivo.In female mammals, dosage compensation is achieved by the transcriptional silencing of one of the two X chromosomes, a process known as X inactivation (1). Features of the inactive X chromosome (Xi) that distinguish it from its active counterpart (Xa) are that it is condensed during interphase, replicates late in S phase, and is underacetylated at histones H3 and H4 (reviewed in ref. 2). More recently it has been shown that chromatin on Xi is highly enriched for the variant histone macroH2A (3).The classically defined X inactivation center (Xic) is required both for initiation of X inactivation in early development and for propagation of the inactivation signal in cis (reviewed in ref. 4). Initiation of random X inactivation involves determining how many (counting) and which (choosing) X chromosome to inactivate. It has been suggested that this is achieved by cells blocking a single Xic and thus marking that chromosome as the active X chromosome. X inactivation then proceeds in cis from unblocked Xics at the onset of cellular differentiation (5).The X inactive specific transcript (Xist) gene, originally identified as a candidate for the Xic (6-9), produces a large RNA with no apparent protein coding potential (10, 11). Xist RNA ''coats'' the inactive X chromosome domain in the interphase nucleus, suggesting that it provides the primary signal for in cis propagation of X inactivation (11,12). A requirement for Xist in propagation of X inactivation in cis has been demonstrated by using targeted deletion of transcribed regions (13,14). Importantly, the counting function of the Xic was unaffected in these experiments. A subsequent genetargeting experiment indicated that sequences distal to Xist are important in counting (15). Analysis of XY embryonic stem (ES) cells bearing a 450-kb Xist yeast artificial chromosome transgene demonstrated that Xist is sufficient for X inactivation (16) and that transgenic loci recapitulate both counting and propagation functions (16,17). This result was subs...

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Section: Resultssupporting

confidence: 81%

Chromatin structure analysis of the mouse Xist locus

McCabe

Formstone²,

O’Neill³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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“…The analysis of the target sequences on the mouse chro mosomes revealed a complex pattern of repeat units encom passing about I million base pairs. Nasir et al (1990) termed the repeat sequence island in the subccntromcric region of the X chromosome a "long complex repeat unit" (LCRU). The results of preliminary sequence analyses of the clone cIOBT33 (data not shown) indicated typical features of the LCRU Sequences described in the mouse.…”

Section: Discussionmentioning

confidence: 99%

Combined Q-banding and fluorescence in situ hybridization for the identification of bovine chromosomes 1 to 7

Solinas‐Toldo¹,

Mezzelani²,

Hawkins³

et al. 1995

Cytogenet Genome Res

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Eleven probes were assigned to bovine chromosomes 1 to 7 by fluorescence in situ hybridization (FISH). The identification of chromosomes was based on QFQ-banding prior to in situ hybridization and comparison with the Reading Conference (1976) and ISCNDA (1989) standards. The probes used for FISH can now be utilized as identification and discrimination features for bovine chromosomes 1 to 7 and particularly for chromosomes 4 and 6, which are difficult to distinguish. Comparison of our mapping data with previous assignments and of the standard chromosome banding patterns prompt us to propose a change in the ISCNDA nomenclature: ISCNDA chromosome 4 should be named chromosome 6 and vice versa. Chromosome 4 is marked by the ribosomal RNA cluster RNR3, and chromosome 6 is characterized by the casein gene cluster and an anonymous satellite (D6Z1).

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“…A localized repeat sequence, DXWas70, maps to the A1/A2 band close to the mouse X Chr centromere (Disteche et al 1985). Finally, a repeat sequence island has been characterized in detail on the mouse X Chr at the A3 G-dark band (Nasir et al 1990(Nasir et al , 1991. The island contains 50 copies of a localized 14-kb-long complex repeat unit, the LCRU, originally identified by the microclone DXSmh141 (Fisher et al 1985).…”

Section: Introductionmentioning

confidence: 99%

“…Aside from centromeric or telomeric regions, a number of euchromatic regions have been identified in mouse chromosomes that are particularly abundant in repeat sequences (Boyle and Ward 1992;Disteche et al 1985;Nasir et al 1990Nasir et al , 1991. These have been termed repeat sequence islands (Nasir et al 1990) and often appear to contain a localized repeat sequence interspersed among common dispersed repetitive elements.…”

Section: Introductionmentioning

confidence: 99%

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YAC clone contigs covering 5 Mb of a repeat sequence island on the mouse X Chromosome

Mileham

Brown

1996

Mammalian Genome

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We have initiated work towards the construction of YAC clone contigs across a repeat sequence island region on the mouse X Chromosome (Chr). The repeat sequence island region-the 141 island-located at band A3 contains 50 copies of a localized long complex repeat unit (LCRU). We have isolated 87 YAC clones from the 141 island and have used a dual faceted approach towards the construction of contigs across the repeat sequence island. First, we have identified YAC clones originating from the same region of the island by the identification of commonly held LCRU restriction site variants. Second, we have constructed rare cutter restriction maps of each YAC clone. Taken together, we have been able to assemble one large contig of 2.8 Mb and a number of smaller contigs. In total, contigs covering 5Mb of the island region have been identified. The island region would appear to represent a major component of the A3 Giemsa dark band on the mouse X Chr.

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Unusual molecular characteristics of a repeat sequence island within a Giemsa-positive band on the mouse X chromosome.

Cited by 27 publications

References 27 publications

Chromatin structure analysis of the mouse Xist locus

Chromatin structure analysis of the mouse Xist locus

Combined Q-banding and fluorescence in situ hybridization for the identification of bovine chromosomes 1 to 7

YAC clone contigs covering 5 Mb of a repeat sequence island on the mouse X Chromosome

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