SEARCH · PubMed Health

Results for “SMC”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1993

Purification and characterization of an autocrine migration factor for vascular smooth muscle cells (SMC), SMC-derived migration factor.

Migration of medial smooth muscle cells (SMC) into the intima is a key step in intimal thickening of atherosclerotic tissues. We previously reported that cultured SMC secrete a potent migration factor for SMC, named SMC-derived migration factor (SDMF). We purified this factor to homogeneity from 20 liters of serum-free conditioned medium of cultured rat aortic SMC by sequential heparin-Sepharose column, red-Sepharose column, TSK-heparin high performance liquid chromatography (HPLC) column, and Superose 6 HPLC column chromatographies. SDMF was found to be a 58-kDa polypeptide by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Reduction by mercaptoethanol caused only a slight decrease in its molecular mass to 53 kDa. Preparative isoelectric focusing revealed that SDMF is a basic protein with a pI of approximately 10. Purified SDMF enhanced the migration of rat SMC dose dependently, its maximal activity being 4 times that of platelet-derived growth factor-BB. In contrast, SDMF did not enhance the migration of endothelial cells from either human umbilical cord vein or rabbit retinal tissue. SDMF had no effect on the proliferation of SMC. These findings suggest that SDMF enhances SMC migration in vascular walls and that the autocrine system of SMC migration contributes to the formation of intimal thickening in atheroma formation.

Animals↗

PubMed1991

Secretion of a potent new migration factor for smooth muscle cells (SMC) by cultured SMC.

Migration of smooth muscle cells (SMC) in the arterial wall is important in the formation of intimal thickening. In this work, cultured SMC from the rat and rabbit aortic media at 2nd to 12th passages were found to secrete a potent migration factor for SMC which was named SMC-derived migration factor (SDMF). This factor stimulated the migration of SMC dose-dependently and its maximum activity was 2-8 times that of PDGF. Checker board analysis showed that SDMF was chemotactic, but not chemokinetic. In further studies, SDMF was found to be inactivated at 100 degrees C for 10 min or by trypsinization, but not inactivated by mercaptoethanol. This factor was not dialyzable. Molecular weight was approximately 500 kDa by a gel filtration. The activity was not inhibited by an anti-PDGF antibody or a fibronectin antiserum. These data suggest that SDMF is a potent migration factor for SMC and that SDMF is distinct from PDGF, fibronectin or other known migration factors. This autocrine system of secretion of SDMF by SMC and its induction of SMC migration may contribute to intimal thickening of the arterial wall in atherosclerosis.

Animals↗

PubMed2002

Condensin architecture and interaction with DNA: regulatory non-SMC subunits bind to the head of SMC heterodimer.

Condensin and cohesin are two protein complexes that act as the central mediators of chromosome condensation and sister chromatid cohesion, respectively. The basic underlying mechanism of action of these complexes remained enigmatic. Direct visualization of condensin and cohesin was expected to provide hints to their mechanisms. They are composed of heterodimers of distinct structural maintenance of chromosome (SMC) proteins and other non-SMC subunits. Here, we report the first observation of the architecture of condensin and its interaction with DNA by atomic force microscopy (AFM). The purified condensin SMC heterodimer shows a head-tail structure with a single head composed of globular domains and a tail with the coiled-coil region. Unexpectedly, the condensin non-SMC trimers associate with the head of SMC heterodimers, producing a larger head with the tail. The heteropentamer is bound to DNA in a distributive fashion, whereas condensin SMC heterodimers interact with DNA as aggregates within a large DNA-protein assembly. Thus, non-SMC trimers may regulate the ATPase activity of condensin by directly interacting with the globular domains of SMC heterodimer and alter the mode of DNA interaction. A model for the action of heteropentamer is presented.

Adenosine Triphosphatases↗

PubMed2006

Optical and resonant X-ray diffraction studies confirm a SmCFI2-SmC liquid crystal phase sequence reversal.

Employing both null transmission ellipsometry and resonant x-ray diffraction, we confirmed the SmC*FI2-SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by two recent theoretical advances. Moreover, the temperature range for the SmC*FI2 phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds.

Journal Article↗

PubMed2005

Dynamic assembly, localization and proteolysis of the Bacillus subtilis SMC complex.

BACKGROUND: SMC proteins are key components of several protein complexes that perform vital tasks in different chromosome dynamics. Bacterial SMC forms a complex with ScpA and ScpB that is essential for chromosome arrangement and segregation. The complex localizes to discrete centres on the nucleoids that during most of the time of the cell cycle localize in a bipolar manner. The complex binds to DNA and condenses DNA in an as yet unknown manner. RESULTS: We show that in vitro, ScpA and ScpB form different complexes with each other, among which the level of the putative 2 ScpA/4 ScpB complex showed a pronounced decrease in level upon addition of SMC protein. Different mutations of the ATPase-binding pocket of SMC reduced, but did not abolish interaction of mutant SMC with ScpA and ScpB. The loss of SMC ATPase activity led to a loss of function in vivo, and abolished proper localization of the SMC complex. The formation of bipolar SMC centres was also lost after repression of gyrase activity, and was abnormal during inhibition of replication, resulting in single central clusters. Resumption of replication quickly re-established bipolar SMC centres, showing that proper localization depends on ongoing replication. We also found that the SMC protein is subject to induced proteolysis, most strikingly as cells enter stationary phase, which is partly achieved by ClpX and LonA proteases. Atomic force microscopy revealed the existence of high order rosette-like SMC structures in vitro, which might explain the formation of the SMC centres in vivo. CONCLUSION: Our data suggest that a ScpA/ScpB sub-complex is directly recruited into the SMC complex. This process does not require SMC ATPase activity, which, however, appears to facilitate loading of ScpA and ScpB. Thus, the activity of SMC could be regulated through binding and release of ScpA and ScpB, which has been shown to affect SMC ATPase activity. The proper bipolar localization of the SMC complex depends on a variety of physiological aspects: ongoing replication, ATPase activity and chromosome supercoiling. Because the cellular concentration of SMC protein is also regulated at the posttranscriptional level, the activity of SMC is apparently regulated at multiple levels.

Adenosine Triphosphatases↗

PubMed2004

Structural biochemistry of ATP-driven dimerization and DNA-stimulated activation of SMC ATPases.

Structural maintenance of chromosome (SMC) proteins play a central role in higher-order chromosome structure in all kingdoms of life. SMC proteins consist of a long coiled-coil domain that joins an ATP binding cassette (ABC) ATPase domain on one side and a dimerization domain on the other side. SMC proteins require ATP binding or hydrolysis to promote cohesion and condensation, which is suggested to proceed via formation of SMC rings or assemblies. To learn more about the role of ATP in the architecture of SMC proteins, we report crystal structures of nucleotide-free and ATP bound P. furiosus SMC ATPase domains. ATP dimerizes two SMC ATPase domains by binding to opposing Walker A and signature motifs, indicating that ATP binding can directly assemble SMC proteins. DNA stimulates ATP hydrolysis in the engaged SMC ABC domains, suggesting that ATP hydrolysis can be allosterically regulated. Structural and mutagenesis data identify an SMC protein conserved-arginine finger that is required for DNA stimulation of the ATPase activity and directly connects a putative DNA interaction site to ATP. Our results suggest that stimulation of the SMC ATPase activity may be a specific feature to regulate the ATP-driven assembly and disassembly of SMC proteins.

Adenosine Triphosphatases↗

PubMed2004

Identification of novel eubacteria from spent mushroom compost (SMC) waste by DNA sequence typing: ecological considerations of disposal on agricultural land.

A small study was undertaken to examine the microbiological characteristics of spent mushroom compost (SMC), which is the major waste by-product of the mushroom industry and which is regularly disposed off by application to agricultural land. The primary aim of this study was to examine SMC for the presence of faecal bacterial pathogens, including Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Secondly it was desirable to quantify bacterial and fungal populations within SMC, and also qualitatively identify the diversity of bacterial populations within SMC, through employment of rDNA PCR and direct sequencing techniques on the culturable microflora. Conventional microbiological analyses of SMC material (n=30) from six commercial operations in both Northern Ireland and the Republic of Ireland, failed to detect Salmonella spp, Listeria spp. or Campylobacter spp. in any of the SMC material examined. Total aerobic plate counts gave a mean count of log10 7.01 colony forming units (cfu) per gram SMC material (range: log10 6.53-7.52 cfu/g). Fungal counts gave a mean count of log(10) 4.57 cfu per gram SMC material (range: log10 3.93-4.98 cfu/g). From a total of greater than 50 colony picks, a total of 12 bacterial morphotypes were identified and were further examined by employment of partial 16S rRNA gene amplification and sequencing techniques, yielding several genera and species, including Bacillus licheniformis, Bacillus subtilis, Klebsiella/Enterobacter sp. Microbacterium sp. Paenibacillus lentimorbus, Pseudomonas mevalonii, Sphingobacterium multivorum and Stenotrophomonas sp. This is the first preliminary report on the microbial diversity of SMC waste and demonstrates the presence of several species that have not been previously described in SMC, in addition to two potentially novel species within the genera Microbacterium and Stenotrophomonas. It is thereby important to examine the ecological microbe-microbe and plant-microbe interactions that are occurring between the native bacterial soil flora and those added annually (theoretically estimated at approximately 10(18) cells) through the application of SMC. Such studies would be beneficial in helping to ascertain the ecological consequences involved in the disposal of SMC waste on agricultural land.

Agaricales↗

PubMed2002

Discovery of two novel families of proteins that are proposed to interact with prokaryotic SMC proteins, and characterization of the Bacillus subtilis family members ScpA and ScpB.

Structural maintenance of chromosomes (SMC) proteins are present in all eukaryotes and in many prokaryotes. Eukaryotic SMC proteins form complexes with various non-SMC subunits, which affect their function, whereas the prokaryotic homologues had no known non-SMC partners and were thought to act as simple homodimers. Here we describe two novel families of proteins, widespread in archaea and (Gram-positive) bacteria, which we denote 'segregation and condensation proteins' (Scps). ScpA genes are localized next to smc genes in nearly all SMC- containing archaea, suggesting that they belong to the same operon and are thus involved in a common process in the cell. The function of ScpA was studied in Bacillus subtilis, which also harbours a well characterized smc gene. Here we show that scpA mutants display characteristic phenotypes nearly identical to those of smc mutants, including temperature- sensitive growth, production of anucleate cells, formation of aberrant nucleoids, and chromosome splitting by the so-called guillotine effect. Thus, both SMC and ScpA are required for chromosome segregation and condensation. Interestingly, mutants of another B. subtilis gene, scpB, which is localized downstream from scpA, display the same phenotypes, which indicate that ScpB is also involved in these functions. ScpB is generally present in species that also encode ScpA. The physical interaction of ScpA and SMC was proven (i) by the use of the yeast two-hybrid system and (ii) by the isolation of a complex containing both proteins from cell extracts of B. subtilis. By extension, we speculate that interaction of orthologues of the two proteins is important for chromosome segregation in many archaea and bacteria, and propose that SMC proteins generally have non-SMC protein partners that affect their function not only in eukaryotes but also in prokaryotes.

Amino Acid Sequence↗

PubMed2002

Differential PDGF secretion by graft and aortic SMC in response to oxidized LDL.

Smooth muscle cells (SMC) from prosthetic vascular grafts constitutively secrete higher levels of platelet-derived growth factor-AA (PDGF-AA) than aortic SMC. Lipid oxidation products accumulate in grafts and may stimulate PDGF production. The effect of oxidized low-density lipoprotein (oxLDL) on PDGF-AA secretion by aortic and graft SMC was compared. SMC isolated from canine thoracic aorta or Dacron thoracoabdominal grafts (n = 10) were incubated with native LDL or oxLDL (0-400 microg/ml) for 72 h. PDGF-AA in the conditioned medium was measured with enzyme-linked immunosorbent assay. OxLDL increased PDGF-AA production by graft SMC from 78 +/- 2 to 256 +/- 16 pg PDGF/microg DNA and aortic SMC from 21 +/- 1 to 40 +/- 2 pg PDGF/microg DNA. Native LDL had no effect. N-acetylcysteine inhibited oxLDL-induced PDGF increase. Both superoxide and H(2)O(2) stimulated PDGF secretion by graft SMC had little effect on aortic SMC. Our results suggest that PDGF production by graft (synthetic) SMC is more sensitive to stimulation by oxidative stress than aortic (contractile) SMC. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress, which stimulates PDGF production by graft SMC. PDGF can induce migration of aortic SMC onto the graft, contributing to the development of intimal hyperplasia.

Animals↗

PubMed2002

Subcellular localization of the Bacillus subtilis structural maintenance of chromosomes (SMC) protein.

The Bacillus subtilis structural maintenance of chromosomes (SMC) protein is a member of a large family of proteins involved in chromosome organization. We found that SMC is a moderately abundant protein ( approximately 1000 dimers per cell). In vivo cross-linking and immunoprecipitation assays revealed that SMC binds to many regions on the chromosome. Visualization of SMC in live cells using a fusion to the green fluorescent protein (GFP) and in fixed cells using immunofluorescence microscopy indicated that a portion of SMC localizes as discrete foci in positions similar to that of the DNA replication machinery (replisome). When visualized simultaneously, SMC and the replisome were often in similar regions of the cell but did not always co-localize. Persistence of SMC foci did not depend on ongoing replication, but did depend on ScpA and ScpB, two proteins thought to interact with SMC. Our results indicate that SMC is bound to many sites on the chromosome and a concentration of SMC is localized near replication forks, perhaps there to bind and organize newly replicated DNA.

Adhesins, Bacterial↗

PubMed2003

Condensin but not cohesin SMC heterodimer induces DNA reannealing through protein-protein assembly.

Condensin and cohesin are chromosomal protein complexes required for chromosome condensation and sister chromatid cohesion, respectively. They commonly contain the SMC (structural maintenance of chromosomes) subunits consisting of a long coiled-coil with the terminal globular domains and the central hinge. Condensin and cohesin holo-complexes contain three and two non-SMC subunits, respectively. In this study, DNA interaction with cohesin and condensin complexes purified from fission yeast was investigated. The DNA reannealing activity is strong for condensin SMC heterodimer but weak for holo-condensin, whereas no annealing activity is found for cohesin heterodimer SMC and Rad21-bound heterotrimer complexes. One set of globular domains of the same condensin SMC is essential for the DNA reannealing activity. In addition, the coiled-coil and hinge region of another SMC are needed. Atomic force microscopy discloses the molecular events of DNA reannealing. SMC assembly that occurs on reannealing DNA seems to be a necessary intermediary step. SMC is eliminated from the completed double-stranded DNA. The ability of heterodimeric SMC to reanneal DNA may be regulated in vivo possibly through the non-SMC heterotrimeric complex.

Adenosine Triphosphatases↗

PubMed2000

Bacillus subtilis SMC is required for proper arrangement of the chromosome and for efficient segregation of replication termini but not for bipolar movement of newly duplicated origin regions.

SMC protein is required for chromosome condensation and for the faithful segregation of daughter chromosomes in Bacillus subtilis. The visualization of specific sites on the chromosome showed that newly duplicated origin regions in growing cells of an smc mutant were able to segregate from each other but that the location of origin regions was frequently aberrant. In contrast, the segregation of replication termini was impaired in smc mutant cells. This analysis was extended to germinating spores of an smc mutant. The results showed that during germination, newly duplicated origins, but not termini, were able to separate from each other in the absence of SMC. Also, DAPI (4',6'-diamidino-2-phenylindole) staining revealed that chromosomes in germinating spores were able to undergo partial or complete replication but that the daughter chromosomes were blocked at a late stage in the segregation process. These findings were confirmed by time-lapse microscopy, which showed that after duplication in growing cells the origin regions underwent rapid movement toward opposite poles of the cell in the absence of SMC. This indicates that SMC is not a required component of the mitotic motor that initially drives origins apart after their duplication. It is also concluded that SMC is needed to maintain the proper layout of the chromosome in the cell and that it functions in the cell cycle after origin separation but prior to complete segregation or replication of daughter chromosomes. It is proposed here that chromosome segregation takes place in at least two steps: an SMC-independent step in which origins move apart and a subsequent SMC-dependent step in which newly duplicated chromosomes condense and are thereby drawn apart.

Bacillus subtilis↗

PubMed2003

Cell-cycle-regulated expression and subcellular localization of the Caulobacter crescentus SMC chromosome structural protein.

Structural maintenance of chromosomes proteins (SMCs) bind to DNA and function to ensure proper chromosome organization in both eukaryotes and bacteria. Caulobacter crescentus possesses a single SMC homolog that plays a role in organizing and segregating daughter chromosomes. Approximately 1,500 to 2,000 SMC molecules are present per cell during active growth, corresponding to one SMC complex per 6,000 to 8,000 bp of chromosomal DNA. Although transcription from the smc promoter is induced during early S phase, a cell cycle transcription pattern previously observed with multiple DNA replication and repair genes, the SMC protein is present throughout the entire cell cycle. Examination of the intracellular location of SMC showed that in swarmer cells, which do not replicate DNA, the protein forms two or three foci. Stalked cells, which are actively engaged in DNA replication, have three or four SMC foci per cell. The SMC foci appear randomly distributed in the cell. Many predivisional cells have bright polar SMC foci, which are lost upon cell division. Thus, chromosome compaction likely involves dynamic aggregates of SMC bound to DNA. The aggregation pattern changes as a function of the cell cycle both during and upon completion of chromosome replication.

Bacterial Proteins↗

PubMed1999

Expression of monocyte chemoattractant protein-1 cDNA in vascular smooth muscle cells: induction of the synthetic phenotype: a possible clue to SMC differentiation in the process of atherogenesis.

In the arterial wall, smooth muscle cells (SMC) normally exist in a quiescent, differentiated state, representing the contractile phenotype. During the development of atherosclerosis SMC change towards the synthetic phenotype going along with proliferation, chemotactic response and increased monocyte binding. Expression of monocyte chemoattractant protein-1 (MCP-1), a potent chemoattractant for monocytes, has been shown to be among the earliest events in atherogenesis. We investigated the effect of MCP-1 on differentiated and dedifferentiated SMC. Differentiation of SMC was induced using Matrigel as a matrix for cultivation. MCP-1 was expressed in SMC by means of a recombinant adenovirus. Expression of MCP-1 led to dedifferentiation of SMC as demonstrated by induction of cytokeratin 18, a marker for the synthetic phenotype. Concurrently, migration was only detectable in MCP-1 expressing cells, whereas SMC infected with a control virus, coding for the nuclear-targeted lacZ gene showed no migration. The expression of intercellular adhesion molecule-1 (ICAM-1) could be demonstrated in synthetic SMC and was induced after infection of differentiated cells with recombinant adenovirus, coding for MCP-1 (AdMCP-1). Expression of ICAM-1 was associated with a tenfold higher monocyte binding compared to lacZ infected cells. Our data suggest that MCP-1 plays an important role for SMC in the functional switch from the contractile to the synthetic phenotype in the course of atherogenesis.

Adenoviridae↗

PubMed2005

Genetic interaction of the SMC complex with topoisomerase IV in Bacillus subtilis.

The role of topoisomerase IV (Topo IV) and of the structural maintenance of chromosomes (SMC) complex in chromosome compaction and in global protein synthesis was investigated. Lowering of the levels of Topo IV led to chromosome decondensation, while overproduction induced chromosome hyper-compaction, showing that Topo IV has an influence on the compaction of the whole chromosome, in a manner similar to that of the SMC protein, though different in mechanism. Increased synthesis of Topo IV in smc-deleted cells partially rescued the growth and condensation defect of the deletion, but not the segregation defect, revealing that the two systems interact at a genetic level. Two-dimensional gel investigations showed that global protein synthesis is highly aberrant in smc-deleted cells, and, to a different extent, also in cells lacking ScpA or ScpB, which form the SMC complex together with SMC protein. Overproduction of Topo IV partially rescued the defect in protein synthesis in smc mutant cells, indicating that Topo IV can restore the loss of negative supercoiling caused by the absence of SMC protein, but does not fully rescue the segregation defect. The data also show that the SMC protein has a dual function, in chromosome supercoiling and in active segregation.

Bacillus subtilis↗

PubMed1998

Subcellular localization of Bacillus subtilis SMC, a protein involved in chromosome condensation and segregation.

We have investigated the subcellular localization of the SMC protein in the gram-positive bacterium Bacillus subtilis. Recent work has shown that SMC is required for chromosome condensation and faithful chromosome segregation during the B. subtilis cell cycle. Using antibodies against SMC and fluorescence microscopy, we have shown that SMC is associated with the chromosome but is also present in discrete foci near the poles of the cell. DNase treatment of permeabilized cells disrupted the association of SMC with the chromosome but not with the polar foci. The use of a truncated smc gene demonstrated that the C-terminal domain of the protein is required for chromosomal binding but not for the formation of polar foci. Regular arrays of SMC-containing foci were still present between nucleoids along the length of aseptate filaments generated by depleting cells of the cell division protein FtsZ, indicating that the formation of polar foci does not require the formation of septal structures. In slowly growing cells, which have only one or two chromosomes, SMC foci were principally observed early in the cell cycle, prior to or coincident with chromosome segregation. Cell cycle-dependent release of stored SMC from polar foci may mediate segregation by condensation of chromosomes.

Animals↗

PubMed2003

SMC protein complexes and the maintenance of chromosome integrity.

Structural maintenance of chromosomes (SMC) family proteins have attracted much attention for their unique protein structure and critical roles in mitotic chromosome organization. Elegant genetic and biochemical studies in yeast and Xenopus identified two different SMC heterodimers in two conserved multiprotein complexes termed 'condensin' and 'cohesin'. These complexes are required for mitotic chromosome condensation and sister chromatid cohesion, respectively, both of which are prerequisite to accurate segregation of chromosomes. Although structurally similar, the SMC proteins in condensin and cohesin appear to have distinct functions, whose specificity and cell cycle regulation are critically determined by their interactions with unique sets of associated proteins. Recent studies of subcellular localization of SMC proteins and SMC-containing complexes, identification of their interactions with other cellular factors, and discovery of new SMC family members have uncovered unexpected roles for SMC proteins and SMC-containing complexes in different aspects of genome functions and chromosome organization beyond mitosis, all of which are critical for the maintenance of chromosome integrity.

Adenosine Triphosphatases↗

PubMed2002

Effect of oxLDL on the uptake and clearance rate of cholesterol in v-SMC originated from human apoA1 transgenic mice.

OBJECTIVE: To study the inhibition effect of oxLDL on the uptake and clearance of intra-cellular (3)H-cholesterol in v-SMC from the human-apoA1 transgenic mice (C57BL/6) and the changes in human-apoA1 mRNA expression in v-SMC from human apoA1 transgenic mice after oxLDL stimulation. METHODS: v-SMC originally isolated from human apoA1 transgenic mice connected with a recombined mouse metallothionein-I (MT-I) promoter was used, and the effect of oxLDL on the uptake and clearance of intracellular (3)H-cholesterol was studied in v-SMC of the transgenic and control mice respectively, the study of h-apoA I mRNA expression from v-SMC of the transgenic mice were done by RT-PCR and Northern blot. RESULTS: oxLDL (30 microg/ml) strongly promoted the SMC proliferation. No difference was found in (3)H-cholesterol uptake between nSMC and trSMC, and the uptake rates of both kinds of SMC rose 100% after oxLDL stimulation. The efflux rates of (3)H-cholesterol in trSMC were much higher than those of nSMC (40% - 50%). After oxLDL stimulation, the clearance rates fell by 28% and 10%, respectively, for nSMC and trSMC. The result of RT-PCR and Northern blot showed that h-apoA1 gene expression was markedly increased by the stimulation of oxLDL. CONCLUSION: Expression of the h-apoA1 gene in C57BL/6 mice enables them to reduce the accumulation of cholesterol in v-SMC. The trSMC can alleviate the harmful effect of oxLDL due to the increase of h-apoA1 expression.

Animals↗