|
Polycomb
Polycomb-group proteins (PcG proteins) are a family of protein complexes first discovered in fruit flies that can remodel chromatin such that epigenetic silencing of genes takes place. Polycomb-group proteins are well known for silencing Hox genes through modulation of chromatin structure during embryonic development in fruit flies (''Drosophila melanogaster''). They derive their name from the fact that the first sign of a decrease in PcG function is often a homeotic transformation of posterior legs towards anterior legs, which have a characteristic comb-like set of bristles. In insects In ''Drosophila'', the Trithorax-group (trxG) and Polycomb-group (PcG) proteins act antagonistically and interact with chromosomal elements, termed Cellular Memory Modules (CMMs). Trithorax-group (trxG) proteins maintain the active state of gene expression while the Polycomb-group (PcG) proteins counteract this activation with a repressive function that is stable over many cell generations and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycomb Group Proteins And Cancer
Polycomb-group proteins (PcG proteins) are a protein family, family of protein complexes first discovered in fruit flies that can remodel chromatin such that epigenetic silencing of genes takes place. Polycomb-group proteins are well known for silencing Hox genes through modulation of chromatin structure during embryonic development in fruit flies (''Drosophila melanogaster''). They derive their name from the fact that the first sign of a decrease in PcG function is often a homeotic transformation of posterior legs towards anterior legs, which have a characteristic comb-like set of bristles. In insects In ''Drosophila'', the Trithorax-group proteins, Trithorax-group (trxG) and Polycomb-group (PcG) proteins act antagonistically and interact with chromosomal elements, termed Cellular Memory Modules (CMMs). Trithorax-group (trxG) proteins maintain the active state of gene expression while the Polycomb-group (PcG) proteins counteract this activation with a repressive function that i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BMI1
Polycomb complex protein BMI-1 also known as polycomb group RING finger protein 4 (PCGF4) or RING finger protein 51 (RNF51) is a protein that in humans is encoded by the ''BMI1'' gene (B cell-specific Moloney murine leukemia virus integration site 1). BMI1 is a polycomb ring finger oncogene. Function BMI1 (B lymphoma Mo-MLV insertion region 1 homolog) has been reported as an oncogene by regulating p16 and p19, which are cell cycle inhibitor genes. Bmi1 knockout in mice results in defects in hematopoiesis, skeletal patterning, neurological functions, and development of the cerebellum. Recently it has been reported that BMI1 is rapidly recruited to sites of DNA damage, where it sustains for over 8h. Loss of BMI1 leads to radiation sensitive and impaired repair of DNA double-strand breaks by homologous recombination. Bmi1 is necessary for efficient self-renewing cell divisions of adult hematopoietic stem cells as well as adult peripheral and central nervous system neural ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trithorax-group Proteins
Trithorax-group proteins (TrxG) are a heterogeneous collection of proteins whose main action is to maintain gene expression. They can be categorized into three general classes based on molecular function: # histone-modifying TrxG proteins # chromatin-remodeling TrxG proteins # DNA-binding TrxG proteins, plus other TrxG proteins not categorized in the first three classes. Discovery The founding member of TrxG proteins, trithorax (trx), was discovered ~1978 by Philip Ingham as part of his doctoral thesis while a graduate student in the laboratory of J.R.S. Whittle at the University of Sussex. Histone-lysine ''N''-methyltransferase 2A is the human homolog of trx. The table contains names of Drosophila TrxG members. Homologs in other species may have different names. Function Trithorax-group proteins typically function in large complexes formed with other proteins. The complexes formed by TrxG proteins are divided into two groups: histone-modifying complexes and ATP-depend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycomb Recruitment In X Chromosome Inactivation
X chromosome inactivation (XCI) is the phenomenon that has been selected during the evolution to balance X-linked gene dosage between XX females and XY males. Phases XCI is usually divided in two phases, the establishment phase when gene silencing is reversible, and maintenance phase when gene silencing becomes irreversible. During the establishment phase of X Chromosome Inactivation (XCI), Xist RNA, the master regulator of this process, is monoallelically upregulated and it spreads ''in cis'' along the future inactive X (Xi), relocates to the nuclear periphery. and recruits repressive chromatin-remodelling complexes Among these, Xist recruits proteins of the Polycomb repressive complexes. Whether Xist directly recruits Polycomb repressive complex 2 (PRC2) to the chromatin or this recruitment is the consequence of Xist-mediated changes on the chromatin has been object of intense debate. Mechanism Some studies showed that PRC2 components are not associated with Xist RNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PRC2
PRC2 (polycomb repressive complex 2) is one of the two classes of polycomb-group proteins or (PcG). The other component of this group of proteins is PRC1 ( Polycomb Repressive Complex 1). This complex has histone methyltransferase activity and primarily methylates histone H3 on lysine 27 (i.e. H3K27me3), a mark of transcriptionally silent chromatin. PRC2 is required for initial targeting of genomic region (PRC Response Elements or PRE) to be silenced, while PRC1 is required for stabilizing this silencing and underlies cellular memory of silenced region after cellular differentiation. PRC1 also mono-ubiquitinates histone H2A on lysine 119 (H2AK119Ub1). These proteins are required for long term epigenetic silencing of chromatin and have an important role in stem cell differentiation and early embryonic development. PRC2 are present in most multicellular organisms. The mouse PRC2 has four subunits: Suz12 (zinc finger), Eed, Ezh1 or Ezh2 ( SET domain with histone methyltrans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PHC1
Polyhomeotic-like protein 1 is a protein that in humans is encoded by the ''PHC1'' gene. Function This gene is a homolog of the ''Drosophila'' polyhomeotic gene, which is a member of the Polycomb group of genes. The gene product is a component of a multimeric protein complex that contains EDR2 and the vertebrate Polycomb protein BMI1. The gene product, the EDR2 protein, and the ''Drosophila'' polyhomeotic protein share two highly conserved domains, named homology domains I and II. These domains are involved in protein–protein interactions and may mediate heterodimerization of the protein encoded by this gene and the EDR2 protein. Mutations in this gene have been associated to cases of primary microcephaly Microcephaly (from Neo-Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it m .... Interactions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycomb Repressive Complex 1
Polycomb repressive complex 1 (PRC1) is one of the two classes of Polycomb Repressive complexes, the other being PRC2. Polycomb-group proteins play a major role in transcriptional regulation during development. Polycomb Repressive Complexes PRC1 and PRC2 function in the silencing of expression of the Hox gene network involved in development as well as the inactivation of the X chromosome. PRC1 inhibits the activated form of RNA polymerase II preinitiation complex with the use of H3K27me. PRC1 binds to three nucleosomes, this is believed to limit access of transcription factors to the chromatin, and therefore limit gene expression Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ....{{Cite journal, last1=Lehmann, first1=Lynn, last2=Ferrari, first2=Roberto, last3=Vashisht, first3=A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell or ovum (: ova) is the female Reproduction, reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized, the oosphere becomes the oospore. When egg and sperm fuse together during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living [animal comes from] an egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatin
Chromatin is a complex of DNA and protein found in eukaryote, eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in reinforcing the DNA during cell division, preventing DNA repair#DNA damage, DNA damage, and regulating gene expression and DNA replication. During mitosis and meiosis, chromatin facilitates proper segregation of the chromosomes in anaphase; the characteristic shapes of chromosomes visible during this stage are the result of DNA being coiled into highly condensed chromatin. The primary protein components of chromatin are histones. An octamer of two sets of four histone cores (Histone H2A, Histone H2B, Histone H3, and Histone H4) bind to DNA and function as "anchors" around which the strands are wound.Maeshima, K., Ide, S., & Babokhov, M. (2019). Dynamic chromatin organization without the 30 nm fiber. ''Current opinion in cell biolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-inactivation
X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation). The choice of which X chromosome will be inactivated in a particular embryonic cell is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism (its cell line). The result is that the choice of inactivated X chromosome in all the cells of the organism is a random distribution, often with about half the cells having the paternal X chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalent Chromatin
Bivalent chromatin are segments of DNA, bound to histone proteins, that have both repressing and activating epigenetic regulators in the same region. These regulators work to enhance or silence the expression of genes. Since these regulators work in opposition to each other, they normally interact with chromatin at different times. However, in bivalent chromatin, both types of regulators are interacting with the same domain at the same time. Bivalent chromatin domains are normally associated with promoters of transcription factor genes that are expressed at low levels. Bivalent domains have also been found to play a role in developmental regulation in pluripotent embryonic stems cells, gene imprinting and cancer. Bivalent epigenetic regulators The most common antagonistic epigenetic regulators found together on bivalent chromatin domains are methylation marks on histone 3 lysine 4 (H3K4me3) and histone 3 lysine 27 (H3K27me3). The H3K27me3 mark silences the gene while the H3K4me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hox Gene
Hox genes, a subset of homeobox, homeobox genes, are a gene cluster, group of related genes that Evolutionary developmental biology, specify regions of the body plan of an embryo along the craniocaudal axis, head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the correct structures form in the correct places of the body. For example, Hox genes in insects specify which appendages form on a segment (for example, legs, antennae, and wings in fruit flies), and Hox genes in vertebrates specify the types and shape of vertebrae that will form. In segmented animals, Hox proteins thus confer segmental or positional identity, but do not form the actual segments themselves. Studies on Hox genes in ciliated larvae have shown they are only expressed in future adult tissues. In larvae with gradual metamorphosis the Hox genes are activated in tissues of the larval body, generally in the trunk region, that will be maintained through metamorp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
