Analysis of fragments of human ribosomal intergenic spacer observed in chromosomes carrying no nucleolar organizer regions

Abstract Hordeum vulgare and Hordeum bulbosum are two closely related barley species, which share a common H genome. H. vulgare has two nucleolar organizer regions (NORs), while the NOR of H. bulbosum is only one. We sequenced the 2.5 kb 25S-18S region in the rDNA of H. bulbosum and compared it to the same region in H. vulgare as well as to the other Triticeae. The region includes an intergenic spacer (IGS) with a number of subrepeats, a promoter, and an external transcribed spacer (5′ETS). The IGS of H. bulbosum downstream of 25S rRNA contains two 143-bp repeats and six 128-bp repeats. In contrast, the IGS in H. vulgare contains an array of seven 79-bp repeats and a varying number of 135-bp repeats. The 135-bp repeats in H. vulgare and the 128-bp repeats in H. bulbosum show similarity. Compared to H. vulgare, the 5′ETS of H. bulbosum is shorter. Additionally, the 5′ETS regions in H. bulbosum and H. vulgare diverged faster than in other Triticeae genera. Alignment of the Triticeae promoter sequences suggests that in Hordeum, as in diploid Triticum, transcription starts with guanine and not with adenine as it is in many other plants.

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Dynamic Changes in the Distribution of a Satellite Homologous to Intergenic 26-18S rDNA Spacer in the Evolution of Nicotiana

Genetics ◽

10.1093/genetics/166.4.1935 ◽

2004 ◽

Vol 166 (4) ◽

pp. 1935-1946

Author(s):

K Y Lim ◽

K Skalicka ◽

B Koukalova ◽

R A Volkov ◽

R Matyasek ◽

...

Keyword(s):

18S Rdna ◽

Intergenic Spacer ◽

Nucleolar Organizer ◽

Nucleolar Organizer Regions ◽

Dynamic Nature ◽

Dynamic Changes ◽

Nicotiana Tomentosiformis ◽

Copy Numbers ◽

Location Patterns

Abstract An ∼135-bp sequence called the A1/A2 repeat was isolated from the transcribed region of the 26-18S rDNA intergenic spacer (IGS) of Nicotiana tomentosiformis. Fluorescence in situ hybridization (FISH) and Southern blot analysis revealed its occurrence as an independent satellite (termed an A1/A2 satellite) outside of rDNA loci in species of Nicotiana section Tomentosae. The chromosomal location, patterns of genomic dispersion, and copy numbers of its tandemly arranged units varied between the species. In more distantly related Nicotiana species the A1/A2 repeats were found only at the nucleolar organizer regions (NOR). There was a trend toward the elimination of the A1/A2 satellite in N. tabacum (tobacco), an allotetraploid with parents closely related to the diploids N. sylvestris and N. tomentosiformis. This process may have already commenced in an S3 generation of synthetic tobacco. Cytosine residues in the IGS were significantly hypomethylated compared with the A1/A2 satellite. There was no clear separation between the IGS and satellite fractions in sequence analysis of individual clones and we found no evidence for CG suppression. Taken together the data indicate a dynamic nature of the A1/A2 repeats in Nicotiana genomes, with evidence for recurrent integration, copy number expansions, and contractions.

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UBF Binding In Vivo Is Not Restricted to Regulatory Sequences within the Vertebrate Ribosomal DNA Repeat

Molecular and Cellular Biology ◽

10.1128/mcb.22.2.657-668.2002 ◽

2002 ◽

Vol 22 (2) ◽

pp. 657-658 ◽

Cited By ~ 155

Author(s):

Audrey C. O’Sullivan ◽

Gareth J. Sullivan ◽

Brian McStay

Keyword(s):

Ribosomal Dna ◽

Intergenic Spacer ◽

Nucleolar Organizer ◽

Nucleolar Organizer Regions ◽

Regulatory Sequences ◽

Structural Role ◽

Binding Characteristics ◽

Dna Repeat

ABSTRACT The HMG box containing protein UBF binds to the promoter of vertebrate ribosomal repeats and is required for their transcription by RNA polymerase I in vitro. UBF can also bind in vitro to a variety of sequences found across the intergenic spacer in Xenopus and mammalian ribosomal DNA (rDNA) repeats. The high abundance of UBF, its colocalization with rDNA in vivo, and its DNA binding characteristics, suggest that it plays a more generalized structural role over the rDNA repeat. Until now this view has not been supported by any in vivo data. Here, we utilize chromatin immunoprecipitation from a highly enriched nucleolar chromatin fraction to show for the first time that UBF binding in vivo is not restricted to known regulatory sequences but extends across the entire intergenic spacer and transcribed region of Xenopus, human, and mouse rDNA repeats. These results are consistent with a structural role for UBF at active nucleolar organizer regions in addition to its recognized role in stable transcription complex formation at the promoter.

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Electron Microscopic investigation of crooke’s change in the pituitaries of patients with hypercorticism

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156225 ◽

1989 ◽

Vol 47 ◽

pp. 848-849

Author(s):

E. Horvath ◽

K. Kovacs ◽

L. Stefaneanu ◽

N. Losinski

Keyword(s):

Nucleolar Organizer ◽

Microscopic Investigation ◽

Electron Microscopic Investigation ◽

Ectopic Acth Syndrome ◽

Nucleolar Organizer Regions ◽

Electron Microscopic ◽

Human Pituitary ◽

Ectopic Acth ◽

Crooke’S Hyalinization

Human pituitary corticotropins have unique morphologic markers: bundles of type-1 filaments, measuring approximately 70 A in width and representing cytokeratin. The extreme ring-like accumulation of type-1 filaments, known as Crooke's hyalinization, signals functional suppression of the corticotropins and occurs in endogenous and exogenous glucocorticoid excess, caused by ACTH-secreting pituitary adenoma, glucocorticoid secreting adrenocortical tumor, ectopic ACTH-syndrome and administration of pharmacologic doses of glucocorticoids. Cells of autonomous corticotroph adenomas usually do not show Crooke's hyalin change. A minority of these tumors, however, retains sensitivity to the negative feed-back effect of elevated blood glucocorticoid levels and display typical Crooke’s change.In the present study pituitary corticotropins in various phases of Crooke's hyalinization were investigated in patients with glucocorticoid excess of various origin, applying histology, immunocytochemistry, count of argyrophilic nucleolar organizer regions (AgNOR), and transmission electron microscopy.

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A role for upstream binding factor in organizing ribosomal gene chromatin

Biochemical Society Symposium ◽

10.1042/bss0730077 ◽

2006 ◽

Vol 73 ◽

pp. 77-84 ◽

Cited By ~ 14

Author(s):

Jane E. Wright ◽

Christine Mais ◽

José-Luis Prieto ◽

Brian McStay

Keyword(s):

Nucleolar Organizer ◽

Ribosomal Gene ◽

Rna Polymerase I ◽

Nucleolar Organizer Regions ◽

Binding Factor ◽

Upstream Binding Factor ◽

Acrocentric Chromosomes ◽

Polymerase I ◽

Secondary Constrictions ◽

Active Nors

Human ribosomal genes are located in NORs (nucleolar organizer regions) on the short arms of acrocentric chromosomes. During metaphase, previously active NORs appear as prominent chromosomal features termed secondary constrictions, which are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I transcription factor UBF (upstream binding factor) binds extensively across the ribosomal gene repeat throughout the cell cycle. Evidence that UBF underpins NOR structure is provided by an examination of cell lines in which large arrays of a heterologous UBF binding sequences are integrated at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus, and during metaphase form novel silver-stainable secondary constrictions, termed pseudo-NORs, that are morphologically similar to NORs.

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Structure and variability of nucleolar organizer regions in Parodontidae fish

Canadian Journal of Genetics and Cytology ◽

10.1139/g84-089 ◽

1984 ◽

Vol 26 (5) ◽

pp. 564-568 ◽

Cited By ~ 51

Author(s):

Orlando Moreira-Filho ◽

Luiz Antonio Carlos Bertollo ◽

Pedro Manoel Galetti Jr.

Keyword(s):

Chromosome Pair ◽

Constitutive Heterochromatin ◽

Nucleolar Organizer ◽

Nucleolar Organizer Regions ◽

Mitotic Chromosomes ◽

Homozygous Condition ◽

Nucleolar Organizing Regions ◽

Nucleolar Chromosome

Nucleolar organizer regions (NORs) were studied in mitotic chromosomes of four species of fish of family Parodontidae: Parodon tortuosus, Apareiodon affinis, Apareiodon ibitiensis, and Apareiodon piracicabae. All four species exhibited only a single nucleolar chromosome pair in their karyotypes. Intraspecific differences were observed in the size of these chromosomes; however, these were not very clear for A. affinis and A. piracicabae, Apareiodon piracicabae exhibited two clearly visible NORs in each of the nucleolar chromosomes, which was the only configuration practically found in this species. This trait therefore predominates in a homozygous condition in the population investigated. Regions of constitutive heterochromatin adjacent to the two NORs were detected. Possible mechanisms that may have originated the two NORs are discussed.Key words: nucleolar organizing regions, fish.

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