Structural features of two major nucleolar organizer regions (NORs), Nor-B1
 and Nor-B2
, and chromosome-specific rRNA gene expression in wheat

The chromosome set of Avena macrostachya Balansa ex Coss. et Durieu was analyzed using C-banding and fluorescence in situ hybridization with 5S and 18S-5.8S-26S rRNA gene probes, and the results were compared with the C-genome diploid Avena L. species. The location of major nucleolar organizer regions and 5S rDNA sites on different chromosomes confirmed the affiliation of A. macrostachya with the C-genome group. However, the symmetric karyotype, the absence of “diffuse heterochromatin”, and the location of large C-band complexes in proximal chromosome regions pointed to an isolated position of A. macrostachya from other Avena species. Based on the distribution of rDNA loci on the C-genome chromosomes of diploid and polyploid Avena species, we propose a model of the chromosome alterations that occurred during the evolution of oat species.

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Detection of nucleolar organizer regions on chromosomes by flourescence in situ hybridization with human 28S rRNA gene and cloning of 28S rRNA gene in Sika deer

Animal Science Journal ◽

10.1111/j.1740-0929.2004.00164.x ◽

2004 ◽

Vol 75 (2) ◽

pp. 111-116 ◽

Cited By ~ 1

Author(s):

Shuuhei KAGEYAMA ◽

Emiko FUKUI ◽

Midori YOSHIZAWA

Keyword(s):

In Situ Hybridization ◽

Sika Deer ◽

Nucleolar Organizer ◽

Nucleolar Organizer Regions ◽

Rrna Gene ◽

28S Rrna ◽

28S Rrna Gene

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Genome Organization in and around the Nucleolus

Cells ◽

10.3390/cells8060579 ◽

2019 ◽

Vol 8 (6) ◽

pp. 579 ◽

Cited By ~ 32

Author(s):

Cristiana Bersaglieri ◽

Raffaella Santoro

Keyword(s):

Cell Fate ◽

Ribosome Biogenesis ◽

Genome Stability ◽

Nuclear Lamina ◽

Nucleolar Organizer ◽

Rrna Genes ◽

Nucleolar Organizer Regions ◽

Rrna Gene ◽

Fate Decision

The nucleolus is the largest substructure in the nucleus, where ribosome biogenesis takes place, and forms around the nucleolar organizer regions (NORs) that comprise ribosomal RNA (rRNA) genes. Each cell contains hundreds of rRNA genes, which are organized in three distinct chromatin and transcriptional states—silent, inactive and active. Increasing evidence indicates that the role of the nucleolus and rRNA genes goes beyond the control of ribosome biogenesis. Recent results highlighted the nucleolus as a compartment for the location and regulation of repressive genomic domains and, together with the nuclear lamina, represents the hub for the organization of the inactive heterochromatin. In this review, we aim to describe the crosstalk between the nucleolus and the rest of the genome and how distinct rRNA gene chromatin states affect nucleolus structure and are implicated in genome stability, genome architecture, and cell fate decision.

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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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Post-Transcriptional Regulation of Cardiac Sarcomere Protein Titin Through 3’ Untranslated Regions

Vanderbilt Undergraduate Research Journal ◽

10.15695/vurj.v9i0.3772 ◽

2013 ◽

Vol 9 ◽

Cited By ~ 1

Author(s):

Tara A Shrout

Keyword(s):

Gene Expression ◽

Transcriptional Control ◽

Striated Muscle ◽

Binding Capacity ◽

Structural Features ◽

Neonatal Rat ◽

Regulatory Control ◽

Untranslated Regions ◽

Luciferase Reporter ◽

Regulatory Effects

Titin is the largest known protein in the human body, and forms the backbone of all striated muscle sarcomeres. The elastic nature of titin is an important component of muscle compliance and functionality. A significant amount of energy is expended to synthesize titin, thus we postulate that titin gene expression is under strict regulatory control in order to conserve cellular resources. In general, gene expression is mediated in part by post-transcriptional control elements located within the 5’ and 3’ untranslated regions (UTRs) of mature mRNA. The 3’UTR in particular contains structural features that affect binding capacity to other RNA components, such as MicroRNA, which control mRNA localization, translation, and degradation. The degree and significance of the regulatory effects mediated by two determined variants of titin’s 3’ UTR were evaluated in Neonatal Rat Ventricular Myocyte and Human Embryonic Kidney cell lines. Recombinant plasmids to transfect these cells lines were engineered by insertion of the variant titin 3’UTR 431- and 1047-base pairs sequences into luciferase reporter vectors. Expression due to an unaltered reporter vector served as the control. Quantitative changes in luciferase activity due to the recombinants proportionally represented the effect titin’s respective 3’UTR conferred on downstream post-transcriptional expression relative to the control. The effect due to titin’s shorter 3’UTR sequence was inconclusive; however, results illustrated that titin’s longer 3’UTR sequence caused a 35 percent decrease in protein expression. Secondary structural analysis of the two sequences revealed differential folding patterns that affect the stability and degree of MicroRNA-binding within titin’s variant 3’UTR sequences.

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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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