| SMC6 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Aliases | SMC6 , SMC-6, SMC6L1, hstructural maintenance of chromosomes 6 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 609387 MGI: 1914491 HomoloGene: 41575 GeneCards: SMC6 | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Structural maintenance of chromosomes protein 6 is a protein that in humans is encoded by the SMC6 gene. [5] [6]
The SMC6 was discovered first in fission yeast as RAD18 (SMC6). It forms a heterodimeric complex with Spr18 (SMC5) protein. [7] [8] In yeast, SMC5/6 complex has sub-units which consists of SMC5, SMC6 and six nonstructural maintenance of chromosomes (NSE) proteins. Nse1-Nse3-Nse4 subunits bridge the Smc5 head Smc6 and allow the binding of DNA. [9] [10] [11]
It is potentially involved in the Alternative lengthening of telomeres cancer mechanism. [12]
Nse1-Nse3-Nse4 subunits bridge the heads of the Smc5 and Smc6 proteins and allow the complex to bind DNA. Nse5 and Nse6 form a sub-complex which localizes to the head of the SMC5/6 complex in the budding yeast Saccharomyces cerevisiae , and to the hinges of the SMC5/6 complex in the fission yeast Schizosaccharomyces pombe . The Nse5/6 sub-complex is required for the replication of S. cerevisiae, but has not been characterized as essential in S. pombe. Orthologous proteins to Nse5-Nse6 exist in other eukaryotes, namely ASAP1-SNI1 in Arabidopsis thaliana and SLF1-SLF2 in humans, which are believed have similar function to their Nse counterparts. The localization of SLF1 and SLF2 on the human SMC5/6 complex is unknown. [13] [14]
The Smc5/6 complex has localization methods which are not heavily conserved. In humans the complex is localized to viral DNA sequences using SMC5/6 localization factors 1 and 2 (SLF1 and SLF2) which contributes to viral resistance. [15] In the plant A. thaliana, this heterodimer can be localized to double stranded breaks for homologous recombination using the SWI3B complex of the SWI/SNF pathway. [16] Once localized to the DNA, the SCM5/6 complex non-specifically binds to ~20 DNA base pairs. [17]
Smc6 and Smc5 proteins form a heterodimeric ring-like structure and together with other non-SMC elements form the SMC-5/6 complex. In the worm Caenorhabditis elegans this complex interacts with the HIM-6(BLM) helicase to promote meiotic recombination intermediate processing and chromosome maturation. [18] The SMC-5/6 complex in mouse oocytes is essential for the formation of segregation competent bivalents during meiosis. [19] In the yeast Saccharomyces cerevisiae , SMC6 is necessary for resistance to DNA damage as well as for damage-induced interchromosomal and sister chromatid recombination. [20] In humans, a chromosome breakage syndrome characterized by severe lung disease in early childhood is associated with a mutation in a component of the SMC-5/6 complex. [21] Patient’s cells display chromosome rearrangements, micronuclei, sensitivity to DNA damage and defective homologous recombination.
Heterochromatin is a tightly packed form of DNA or condensed DNA, which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes. Because it is tightly packed, it was thought to be inaccessible to polymerases and therefore not transcribed; however, according to Volpe et al. (2002), and many other papers since, much of this DNA is in fact transcribed, but it is continuously turned over via RNA-induced transcriptional silencing (RITS). Recent studies with electron microscopy and OsO4 staining reveal that the dense packing is not due to the chromatin.
Schizosaccharomyces pombe, also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. Its genome, which is approximately 14.1 million base pairs, is estimated to contain 4,970 protein-coding genes and at least 450 non-coding RNAs.
Condensins are large protein complexes that play a central role in chromosome assembly and segregation during mitosis and meiosis. Their subunits were originally identified as major components of mitotic chromosomes assembled in Xenopus egg extracts.
Subtelomeres are segments of DNA between telomeric caps and chromatin.
SMC complexes represent a large family of ATPases that participate in many aspects of higher-order chromosome organization and dynamics. SMC stands for Structural Maintenance of Chromosomes.
The replication factor C, or RFC, is a five-subunit protein complex that is required for DNA replication.
Cohesin is a protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping. Cohesin is formed of SMC3, SMC1, SCC1 and SCC3. Cohesin holds sister chromatids together after DNA replication until anaphase when removal of cohesin leads to separation of sister chromatids. The complex forms a ring-like structure and it is believed that sister chromatids are held together by entrapment inside the cohesin ring. Cohesin is a member of the SMC family of protein complexes which includes Condensin, MukBEF and SMC-ScpAB.
Chromosome segregation is the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This segregation process occurs during both mitosis and meiosis. Chromosome segregation also occurs in prokaryotes. However, in contrast to eukaryotic chromosome segregation, replication and segregation are not temporally separated. Instead segregation occurs progressively following replication.
Cell cycle checkpoint protein RAD17 is a protein that in humans is encoded by the RAD17 gene.
DNA repair protein RAD50, also known as RAD50, is a protein that in humans is encoded by the RAD50 gene.
DNA repair protein complementing XP-G cells is a protein that in humans is encoded by the ERCC5 gene.
Cell cycle checkpoint protein RAD1 is a protein that in humans is encoded by the RAD1 gene.
Double-strand-break repair protein rad21 homolog is a protein that in humans is encoded by the RAD21 gene. RAD21, an essential gene, encodes a DNA double-strand break (DSB) repair protein that is evolutionarily conserved in all eukaryotes from budding yeast to humans. RAD21 protein is a structural component of the highly conserved cohesin complex consisting of RAD21, SMC1A, SMC3, and SCC3 [ STAG1 (SA1) and STAG2 (SA2) in multicellular organisms] proteins, involved in sister chromatid cohesion.
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.
Structural maintenance of chromosomes protein 5 is a protein encoded by the SMC5 gene in human.
Meiotic recombination protein REC8 homolog is a protein that in humans is encoded by the REC8 gene.
Sister chromatid cohesion refers to the process by which sister chromatids are paired and held together during certain phases of the cell cycle. Establishment of sister chromatid cohesion is the process by which chromatin-associated cohesin protein becomes competent to physically bind together the sister chromatids. In general, cohesion is established during S phase as DNA is replicated, and is lost when chromosomes segregate during mitosis and meiosis. Some studies have suggested that cohesion aids in aligning the kinetochores during mitosis by forcing the kinetochores to face opposite cell poles.
Condensin-2 complex subunit H2, also known as chromosome-associated protein H2 (CAP-H2) or non-SMC condensin II complex subunit H2 (NCAPH2), is a protein that in humans is encoded by the NCAPH2 gene. CAP-H2 is a subunit of condensin II, a large protein complex involved in chromosome condensation.
Structural maintenance of chromosomes protein 1B (SMC-1B) is a protein that in humans is encoded by the SMC1B gene. SMC proteins engage in chromosome organization and can be broken into 3 groups based on function which are cohesins, condensins, and DNA repair.SMC-1B belongs to a family of proteins required for chromatid cohesion and DNA recombination during meiosis and mitosis. SMC1ß protein appears to participate with other cohesins REC8, STAG3 and SMC3 in sister-chromatid cohesion throughout the whole meiotic process in human oocytes.
RRM3 is a gene that encodes a 5′-to-3′ DNA helicase known affect multiple cellular replication and repair processes and is most commonly studied in Saccharomyces cerevisiae. RRM3 formally stands for Ribosomal DNArecombination mutation 3. The gene codes for nuclear protein Rrm3p, which is 723 amino acids in length, and is part of a Pif1p DNA helicase sub-family that is conserved from yeasts to humans. RRM3 and its encoded protein have been shown to be vital for cellular replication, specifically associating with replication forks genome-wide. RRM3 is located on chromosome 8 in yeast cells and codes for 723 amino acids producing a protein that weighs 81,581 Da.
