Target type: cellularcomponent
A region of a chromosome where nucleoli form during interphase, and where genes encoding the largest rRNA precursor transcript are tandemly arrayed. [PMID:14504406]
The nucleolus organizer region (NOR) is a specific chromosomal region that contains multiple copies of the genes encoding ribosomal RNA (rRNA). These genes are transcribed by RNA polymerase I and are essential for ribosome biogenesis. The NOR is located within the nucleolus, a specialized region within the nucleus that is responsible for ribosome assembly.
The cellular component of the NOR is characterized by a highly organized structure that includes the following elements:
1. **rDNA genes:** The NOR contains multiple copies of the rDNA genes, which are transcribed into rRNA. These genes are organized into tandem repeats, meaning that they are arranged in a head-to-tail fashion.
2. **Ribosomal DNA transcription units:** The rDNA genes are transcribed into rRNA by RNA polymerase I. This process occurs within specific regions of the NOR called transcription units. Each transcription unit contains a promoter region, a coding region, and a terminator region.
3. **Ribosomal proteins:** The rRNA molecules synthesized within the NOR associate with ribosomal proteins to form ribosomes. These proteins are transported to the NOR from the cytoplasm, where they are synthesized.
4. **Nucleolar organizing proteins:** The NOR is also associated with a number of specific proteins that regulate the transcription of rDNA genes and the assembly of ribosomes. These proteins include nucleolin, fibrillarin, and nucleophosmin.
The highly organized structure of the NOR allows for efficient and coordinated rRNA synthesis and ribosome assembly. The presence of multiple rDNA copies within the NOR ensures that sufficient amounts of rRNA are produced to meet the demands of protein synthesis. The specific proteins associated with the NOR play critical roles in regulating this process.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| NAD-dependent protein deacetylase sirtuin-7 | An NAD-dependent protein deacetylase sirtuin-7 that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q9NRC8] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| panobinostat | panobinostat : A hydroxamic acid obtained by formal condensation of the carboxy group of (2E)-3-[4-({[2-(2-methylindol-3-yl)ethyl]amino}methyl)phenyl]prop-2-enoic acid with the amino group of hydroxylamine. A histone deacetylase inhibitor used (as its lactate salt) in combination with bortezomib and dexamethasone for the treatment of multiple myeloma. Panobinostat: An indole and hydroxamic acid derivative that acts as a HISTONE DEACETYLASE inhibitor. It is used as an antineoplastic agent in combination with BORTEZOMIB and DEXAMETHASONE for the treatment of MULTIPLE MYELOMA. | cinnamamides; hydroxamic acid; methylindole; secondary amino compound | angiogenesis modulating agent; antineoplastic agent; EC 3.5.1.98 (histone deacetylase) inhibitor |
| quisinostat | indoles |