![]() NMP-1 is a ubiquitous, cell growth-regulated protein that is related to the transcription factor ATF and resides in both the nuclear matrix and the nonmatrix nuclear compartment. NMP-1 and NMP-2 are two matrix DNA-binding proteins that are sequence-specific and interact with the osteocalcin gene promoter in the osteoblast cells. It interacts with DNA through an ARID or A/T-rich interaction domain, and is DNA-binding protein. Bright, or B cell regulator of immunoglobulin heavy chain transcription, is a B lymphocyte-specific protein first discovered for its ability to increase immunoglobulin transcription three to seven fold in antigen-activated B cells. Additionally, the HMGI(Y) proteins have the ability to interact with various protein transcription factors both in vitro and in vivo. In vitro the HMGI(Y) proteins also have the ability to selectively bind to distorted DNA structures and to bend, unwind, and supercoil DNA substrates. Molecular weight of 120,000 (SP120) coincided with the 365-base pair HindIII-HinfI fragment that had been identified as MAR. īy using a plasmid harboring a portion of the Ig kappa gene within which MAR had been located, searched for proteins recognizing MAR in the nuclear scaffold components. Under conditions of high co-operativity, at input ratios of H1 to DNA was up to 15% (w/w). About one topoisomerase II dimer is bound per 200 bp of DNA Histone H1 specifically associates with SARs, and binds preferentially to those DNA molecules harboring a SAR, leaving the non-SAR fragments free. Purified topoisomerase II preferentially binds SAR-containing DNA.With increasing concentrations of topoisomerase II, the protein titrate quantitatively first SAR-containing DNA and then non-SAR DNA. demonstrated that lamin B1 was a MAR-binding protein by means of a DNA-binding protein blot assay and in vitro binding studies. Competition studies revealed the existence of two different types of interaction related to different structural features of MARs: one involving the minor groove of double-stranded MAR DNA and one involving single-stranded regions. A-type lamins and the structurally related proteins desmin and NuMA also specifically bind MARs in vitro. Of these, 7 were identified as specific DNA binding proteins including lamins A, C, matrins D, E, F, G, and 4. Approximately 12 major proteins were consistently found from the isolated rat liver nuclear matrix. Most MARBPs have been found to be the components of nuclear matrices. A variety of proteins that interact with MARs have been identified from animals, plants, human and algae, the functions of MARBPs may involve in regulation of gene transcription and expression, packaging of chromosome, cell development and cell apoptosis. Until now the mechanism of MAR regulation function is unknown because the limited knowledge about the trans-acting factors. As a cis-regulatory element, the functions of MAR must be relative with its trans-acting factors. DNA replication, transcription, repair, splicing, and recombination seem to take place on the nuclear matrix. Īccording to the current reports, MARs may cohabit with core origin replication (ORIs) and another fraction might cohabit with transcriptional enhancers. MARs appear to be functionally conserved, since animal MARs can bind to plant nuclear scaffolds and vice versa. Of the MAR elements reported, many do not display extensive sequence homology, their DNA sequence is highly polymorphic. A set of 21 characteristics is deduced or proposed for MAR/ORI sequences including their enrichment in inverted repeats, AT tracts, DNA unwinding elements, replication initiator protein sites, homooligonucleotide repeats (i.e., AAA, TTT, CCC), curved DNA, DNase I-hypersensitive sites, nucleosome-free stretches, polypurine stretches, and motifs with a potential for left-handed and triplex structures. MARs are about 200 bp long, AT-rich, contain topoisomerase II consensus sequences and other AT-rich sequence motifs, often reside near cis-acting regulatory sequences, and their binding sites are abundant (greater than 10,000 per mammalian nucleus). DNA sequences that bind preferentially to nuclear matrices are named matrix attachment region (MAR) or scaffold associated region (SAR), which were supposed to mediate this loop formation in vivo. Chromatin is looped into domains by attachment of the chromatin fibre to the nuclear matrix. Nuclear matrices or nuclear scaffold were defined the biochemical fraction of the nucleus after treatment by with detergent, salt and nucleases, mainly consist of non-histone protein, RNA and DNA in the eukaryote.
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