Nuclear matrix

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In biology, the nuclear matrix is the network of fibres found throughout the inside of a cell nucleus after a specific method of chemical extraction. According to some it is somewhat analogous to the cell cytoskeleton. In contrast to the cytoskeleton, however, the nuclear matrix has been proposed to be a dynamic structure. Along with the nuclear lamina, it supposedly aids in organizing the genetic information within the cell. [1]

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The exact function of this structure is still disputed, and its very existence has been called into question. [2] Evidence for such a structure was recognised as long ago as 1948, [3] and consequently many proteins associated with the matrix have been discovered. The presence of intra-cellular proteins is common ground, and it is agreed that proteins such as the Scaffold, or Matrix Associated Proteins (SAR or MAR) have some role in the organisation of chromatin in the living cell. There is evidence that the nuclear matrix is involved in regulation of gene expression in Arabidopsis thaliana . [4]

Whenever a similar structure can actually be found in living cells remains a topic of discussion. [5] According to some sources, most, if not all proteins found in nuclear matrix are the aggregates of proteins of structures that can be found in the nucleus of living cells. Such structures are nuclear lamina, which consist of proteins termed lamins which can be also found in the nuclear matrix. [6]

Validity of nuclear matrix

For a long time the question whether a polymer meshwork, a “nuclear matrix” or “nuclear-scaffold” or "NuMat" is an essential component of the in vivo nuclear architecture has remained a matter of debate. While there are arguments that the relative position of chromosome territories (CTs), the equivalent of condensed metaphase chromosomes at interphase, may be maintained due to steric hindrance or electrostatic repulsion forces between the apparently highly structured CT surfaces, this concept has to be reconciled with observations according to which cells treated with the classical matrix-extraction procedures maintain defined territories up to the point where a minor subset of acidic nuclear matrix proteins is released – very likely those proteins that governed their association with the nuclear skeleton. [7] The nuclear matrix proteome consists of structural proteins, chaperones, DNA/RNA-binding proteins, chromatin remodeling and transcription factors. The complexity of NuMat is an indicator of diverse structural and functional significance of its proteins. [8]

Scaffold/Matrix attachment regions (S/MARs)

S/MARs (scaffold/matrix attachment regions), the DNA regions that are known to attach genomic DNA to variety of nuclear proteins, show an ever increasing spectrum of established biological activities. There is a known overlap of this large group of sequences with sequences termed LADs (lamina attachment domains).

S/MARs find increasing use for the rational design of vectors with widespread use in gene therapy and biotechnology. Nowadays S/MAR functions can be modulated, improved and custom-tailored to the specific needs of novel vector systems. [9]

Nuclear matrix and cancer

The nuclear matrix composition on human cells has been proven to be cell type and tumor specific. It has been clearly demonstrated that the nuclear matrix composition in a tumor is different from its normal counterparts. [10] This fact could be useful to characterize cancer markers and to predict the disease even earlier. These markers have been found in urine and blood and could potentially be used in early detection and prognosis of human cancers.[ citation needed ]

See also

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<i>Arabidopsis thaliana</i> Model plant species in the family Brassicaceae

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<span class="mw-page-title-main">Cytoskeleton</span> Network of filamentous proteins that forms the internal framework of cells

The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms. It is composed of three main components: microfilaments, intermediate filaments, and microtubules, and these are all capable of rapid growth or disassembly depending on the cell's requirements.

<span class="mw-page-title-main">Nucleoplasm</span> Protoplasm that permeates a cells nucleus

The nucleoplasm, also known as karyoplasm, is the type of protoplasm that makes up the cell nucleus, the most prominent organelle of the eukaryotic cell. It is enclosed by the nuclear envelope, also known as the nuclear membrane. The nucleoplasm resembles the cytoplasm of a eukaryotic cell in that it is a gel-like substance found within a membrane, although the nucleoplasm only fills out the space in the nucleus and has its own unique functions. The nucleoplasm suspends structures within the nucleus that are not membrane-bound and is responsible for maintaining the shape of the nucleus. The structures suspended in the nucleoplasm include chromosomes, various proteins, nuclear bodies, the nucleolus, nucleoporins, nucleotides, and nuclear speckles.

<span class="mw-page-title-main">Lamin</span>

Lamins, also known as nuclear lamins are fibrous proteins in type V intermediate filaments, providing structural function and transcriptional regulation in the cell nucleus. Nuclear lamins interact with inner nuclear membrane proteins to form the nuclear lamina on the interior of the nuclear envelope. Lamins have elastic and mechanosensitive properties, and can alter gene regulation in a feedback response to mechanical cues. Lamins are present in all animals but are not found in microorganisms, plants or fungi. Lamin proteins are involved in the disassembling and reforming of the nuclear envelope during mitosis, the positioning of nuclear pores, and programmed cell death. Mutations in lamin genes can result in several genetic laminopathies, which may be life-threatening.

<span class="mw-page-title-main">Nuclear lamina</span>

The nuclear lamina is a dense fibrillar network inside the nucleus of eukaryote cells. It is composed of intermediate filaments and membrane associated proteins. Besides providing mechanical support, the nuclear lamina regulates important cellular events such as DNA replication and cell division. Additionally, it participates in chromatin organization and it anchors the nuclear pore complexes embedded in the nuclear envelope.

<span class="mw-page-title-main">Transfer DNA</span> Type of DNA in bacterial genomes

The transfer DNA is the transferred DNA of the tumor-inducing (Ti) plasmid of some species of bacteria such as Agrobacterium tumefaciens and Agrobacterium rhizogenes . The T-DNA is transferred from bacterium into the host plant's nuclear DNA genome. The capability of this specialized tumor-inducing (Ti) plasmid is attributed to two essential regions required for DNA transfer to the host cell. The T-DNA is bordered by 25-base-pair repeats on each end. Transfer is initiated at the right border and terminated at the left border and requires the vir genes of the Ti plasmid.

<span class="mw-page-title-main">Constitutive heterochromatin</span>

Constitutive heterochromatin domains are regions of DNA found throughout the chromosomes of eukaryotes. The majority of constitutive heterochromatin is found at the pericentromeric regions of chromosomes, but is also found at the telomeres and throughout the chromosomes. In humans there is significantly more constitutive heterochromatin found on chromosomes 1, 9, 16, 19 and Y. Constitutive heterochromatin is composed mainly of high copy number tandem repeats known as satellite repeats, minisatellite and microsatellite repeats, and transposon repeats. In humans these regions account for about 200Mb or 6.5% of the total human genome, but their repeat composition makes them difficult to sequence, so only small regions have been sequenced.

<span class="mw-page-title-main">Protein inhibitor of activated STAT</span>

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<span class="mw-page-title-main">Nuclear envelope</span> Nuclear membrane surrounding the nucleus in eukaryotic cells

The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material.

<span class="mw-page-title-main">HNRPU</span> Protein-coding gene in the species Homo sapiens

Heterogeneous nuclear ribonucleoprotein U is a protein that in humans is encoded by the HNRNPU gene.

<span class="mw-page-title-main">SAFB</span> Protein-coding gene in the species Homo sapiens

Scaffold attachment factor B, also known as SAFB, is a gene with homologs that have been studied in humans and mice.

<span class="mw-page-title-main">Lamin B1</span> Protein-coding gene in the species Homo sapiens

Lamin-B1 is a protein that in humans is encoded by the LMNB1 gene.

<span class="mw-page-title-main">Inner nuclear membrane protein</span> Protein embedded in inner membrane of nuclear envelope

Inner nuclear membrane proteins are membrane proteins that are embedded in or associated with the inner membrane of the nuclear envelope. There are about 60 INM proteins, most of which are poorly characterized with respect to structure and function. Among the few well-characterized INM proteins are lamin B receptor (LBR), lamina-associated polypeptide 1 (LAP1), lamina-associated polypeptide-2 (LAP2), emerin and MAN1.

<span class="mw-page-title-main">Chloroplast DNA</span> DNA located in cellular organelles called chloroplasts

Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nucleus. The existence of chloroplast DNA was identified biochemically in 1959, and confirmed by electron microscopy in 1962. The discoveries that the chloroplast contains ribosomes and performs protein synthesis revealed that the chloroplast is genetically semi-autonomous. The first complete chloroplast genome sequences were published in 1986, Nicotiana tabacum (tobacco) by Sugiura and colleagues and Marchantia polymorpha (liverwort) by Ozeki et al. Since then, a great number of chloroplast DNAs from various species have been sequenced.

<span class="mw-page-title-main">Scaffold/matrix attachment region</span>

The term S/MAR, otherwise called SAR, or MAR, are sequences in the DNA of eukaryotic chromosomes where the nuclear matrix attaches. As architectural DNA components that organize the genome of eukaryotes into functional units within the cell nucleus, S/MARs mediate structural organization of the chromatin within the nucleus. These elements constitute anchor points of the DNA for the chromatin scaffold and serve to organize the chromatin into structural domains. Studies on individual genes led to the conclusion that the dynamic and complex organization of the chromatin mediated by S/MAR elements plays an important role in the regulation of gene expression.

In molecular biology, the protein domain, YTH refers to a member of the YTH family that has been shown to selectively remove transcripts of meiosis-specific genes expressed in mitotic cells.

<span class="mw-page-title-main">Nuclear organization</span> Spatial distribution of chromatin within a cell nucleus

Nuclear organization refers to the spatial distribution of chromatin within a cell nucleus. There are many different levels and scales of nuclear organisation. Chromatin is a higher order structure of DNA.

Decreased DNA Methylation I (DDM1), is a plant gene that encodes a nucleosome remodeler which facilitates DNA methylation. The DDM1 gene has been described extensively in Arabidopsis thaliana and also in maize. The protein has been described to be similar to the SWI2/SNF2 chromatin remodeling proteins.

Plant nucleus movement is the movement of the cell nucleus in plants by the cytoskeleton.

References

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