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Condensin
Condensins are large protein complexes that play a central role in chromosome condensation and segregation during mitosis and meiosis (Figure 1). Their subunits were originally identified as major components of mitotic chromosomes assembled in ''Xenopus'' egg extracts. Subunit composition and phylogeny Eukaryotic types Many eukaryotic cells possess two different types of condensin complexes, known as condensin I and condensin II, each of which is composed of five subunits (Figure 2). Condensins I and II share the same pair of core subunits, SMC2 and SMC4, both belonging to a large family of chromosomal ATPases, known as SMC proteins (SMC stands for Structural Maintenance of Chromosomes). Each of the complexes contains a distinct set of non-SMC regulatory subunits (a kleisin subunit and a pair of HEAT repeat subunits). Both complexes are large, having a total molecular mass of 650-700 kDa. The core subunits condensins (SMC2 and SMC4) are conserved among all eukaryotic spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome Condensation
Chromosome condensation refers to the process by which dispersed interphase chromatin is transformed into a set of compact, rod-shaped structures during mitosis and meiosis (Figure 1). The term "chromosome condensation" has long been used in biology. However, it is now increasingly recognized that mitotic chromosome condensation proceeds through mechanisms distinct from those governing "condensation" in physical chemistry (e.g., gas-to-liquid phase transitions) or the formation of "biomolecular condensates" in cell biology. Consequently, some researchers have argued that the term "chromosome condensation" may be misleading in this context. For this reason, alternative terms such as "chromosome assembly" or "chromosome formation" are also commonly used. Processes of chromosome condensation From DNA to chromosomes A diploid human cell contains 46 chromosomes: 22 pairs of autosomes (22 × 2) and one pair of sex chromosomes (XX or XY). The total length of DNA within a single nucleus re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMC4
Structural maintenance of chromosomes protein 4 (SMC-4) also known as chromosome-associated polypeptide C (CAP-C) or XCAP-C homolog is a protein that in humans is encoded by the ''SMC4'' gene. SMC-4 is a core subunit of condensin I and II, large protein complexes involved in high order chromosome organization, including condensation and segregation. SMC-4 protein is commonly associated with the SMC-2 protein, another protein complex within the SMC protein family. SMC-4 dimerizes with SMC-2, creating the flexible and dynamic structure of the condensin holocomplex. An over-expression of the SMC-4 protein is shown to impact carcinogenesis. Structure and interactions The primary 5 domain structure of SMC proteins is highly conserved among species. The basic structure of SMC proteins are characterized by a non-helical hinge group, separated by two anti-parallel α-helical coiled-coil domains, along with two Amino-terminal globular domains containing ATP hydrolytic sites, or nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMC2
Structural maintenance of chromosomes protein 2 (SMC-2), also known as chromosome-associated protein E (CAP-E), is a protein that in humans is encoded by the ''SMC2'' gene. SMC2 is part of the SMC protein family and is a core subunit of condensin I and II, large protein complexes involved in chromosome condensation, overall organization. Several studies have demonstrated the necessity of SMC2 for cell division and proliferation. Structure As one of the 6 Eukaryotic SMC proteins, SMC2 forms a hetero dimer with SMC4 via their hinge domains. The heterodimer formed functions as a flexible and dynamic holocomplex core, which complexes with variant other non-SMC regulatory proteins to form condensin. In condensin I, SMC2 complexes with CAP-H, CAP-D2, and CAP-G. In condensin II, SMC2 complexes with CAP-H2, CAP-D3, and CAP-G2. Subunits CAP-H and CAP-H2 are categorized as kleisin proteins, similar to Scc1 which is found in cohesin, while CAP-D2, CAP-G, CAP-D3, and CAP-G2 contain str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMC Protein
SMC proteins represent a large family of ATPases that participate in many aspects of higher-order chromosome organization and dynamics. SMC proteins are widely conserved across bacteria, archaea, and eukaryotes. In eukaryotes, they function as the core ATPase subunits of large protein complexes such as condensin, cohesin, and SMC5/6. The term SMC derives from a mutant strain of ''Saccharomyces cerevisiae'' named ''smc1'' (stability of mini-chromosomes 1), which was identified based on its defect in maintaining the stability of mini-chromosomes. After the gene product of ''SMC1'' was characterized, and homologous proteins were found to be essential for chromosome structure and dynamics in many organisms, the acronym SMC was redefined to stand for "Structural Maintenance of Chromosomes". Classification Eukaryotic SMCs Eukaryotes have at least six SMC proteins in individual organisms, and they form three distinct heterodimers with specialized functions: *SMC1-SMC3: A pair of SM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HEAT Repeat
A HEAT repeat is a Protein tandem repeats, protein tandem repeat structural motif composed of two alpha helices linked by a short loop. HEAT repeats can form alpha solenoids, a type of solenoid protein domain found in a number of cytoplasmic proteins. The name "HEAT" is an acronym for four proteins in which this repeat structure is found: huntingtin, Huntingtin, elongation factor 3 (EF3), protein phosphatase 2A (PP2A), and the yeast kinase TOR1. HEAT repeats form extended superhelical structures which are often involved in intracellular transport; they are structurally related to armadillo repeats. The nuclear transport protein KPNB1, importin beta contains 19 HEAT repeats. Various HEAT repeat proteins and their structures Representative examples of HEAT repeat proteins include importin β (also known as karyopherin β) family, regulatory subunits of condensin and cohesin, separase, PIKKs (phosphatidylinositol 3-kinase-related protein kinases) such as ATM (w:Ataxia telangiectasia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenopus Egg Extract
''Xenopus'' egg extract is a lysate that is prepared by crushing the eggs of the African clawed frog ''Xenopus laevis''. It offers a powerful cell-free (or ''in vitro'') system for studying various cell biological processes, including cell cycle progression, nuclear transport, DNA replication and chromosome segregation. It is also called ''Xenopus'' egg cell-free system or ''Xenopus'' egg cell-free extract. History The first frog egg extract was reported in 1983 by Lohka and Masui. This pioneering work used eggs of the Northern leopard frog ''Rana pipiens'' to prepare an extract. Later, the same procedure was applied to eggs of ''Xenopus laevis'', becoming popular for studying cell cycle progression and cell cycle-dependent cellular events. Extracts derived from eggs of the Japanese common toad '' Bufo japonicus'' or of the Western clawed frog ''Xenopus tropicalis'' have also been reported. Basics of extract preparation The cell cycle of unfertilized eggs of ''X. laevis'' is arres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanidioschyzon Merolae
''Cyanidioschyzon merolae'' is a small (2μm), club-shaped, unicellular haploid red alga adapted to high sulfur acidic hot spring environments (pH 1.5, 45 °C). The cellular architecture of ''C. merolae'' is extremely simple, containing only a single chloroplast and a single mitochondrion and lacking a vacuole and cell wall. In addition, the cellular and organelle divisions can be synchronized. For these reasons, ''C. merolae'' is considered an excellent model system for study of cellular and organelle division processes, as well as biochemistry and structural biology. The organism's genome was the first full algal genome to be sequenced in 2004; its plastid was sequenced in 2000 and 2003, and its mitochondrion in 1998. The organism has been considered the simplest of eukaryotic cells for its minimalist cellular organization. Isolation and growth in culture Originally isolated by De Luca in 1978 from the solfatane fumaroles of Campi Flegrei ( Naples, Italy), ''C. merola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome of around 135 Base pair#Length measurements, megabase pairs. It was the first plant to have its genome sequenced, and is an important tool for understanding the molecular biology of many plant traits, including flower development and phototropism, light sensing. Description ''Arabidopsis thaliana'' is an annual plant, annual (rarely biennial plant, biennial) plant, usually growing to 20–25 cm tall. The leaf, leaves form a rosette at the base of the plant, with a few leaves also on the flowering Plant ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paralog
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different wikt:undulating, undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their biological life cycle, life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils, including anoxic and oxygen-depleted habitats. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many Ectosymbiosis, ectosymbiotic and endosymbiotic species, as well as some Obligate parasite, obligate and Facultative paras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paralogs
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties (''p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahymena Thermophila
''Tetrahymena thermophila'' is a species of Ciliophora in the family Tetrahymenidae. It is a free living protozoon and occurs in fresh water. There is little information on the ecology and natural history of this species, but it is the most widely known and widely studied species in the genus '' Tetrahymena''. The species has been used as a model organism for molecular and cellular biology. It has also helped in the discovery of new genes as well as helping to understand the mechanisms of function of certain genes. Studies on this species have contributed to major discoveries in biology. For example, the MAT locus found in this species has provided a foundation for the evolution of mating systems. The species was at first considered to be a form of '' Tetrahymena pyriformis''. '' T. malaccensis'' is the closest relative to''T. thermophila''. Characteristics It is about 50 μm long. One famous trait this species is known for is that has 7 different mating types, unlike ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
