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Trans-regulatory Element
Trans-regulatory elements (TRE) are DNA sequences encoding upstream regulators (ie. trans-acting factors), which may modify or regulate the expression of distant genes. Trans-acting factors interact with cis-regulatory elements to regulate gene expression. TRE mediates expression profiles of a large number of genes via trans-acting factors. While TRE mutations affect gene expression, it is also one of the main driving factors for evolutionary divergence in gene expression. Trans vs cis elements Trans-regulatory elements work through an intermolecular interaction between two different molecules and so are said to be " acting in trans". For example (1) a transcribed and translated transcription factor protein derived from the trans-regulatory element; and a (2) DNA regulatory element that is adjacent to the regulated gene. This is in contrast to cis-regulatory elements that work through an intramolecular interaction between different parts of the same molecule: (1) a gene; and ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulation Of Gene Expression
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network. Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (''Ac'') and Dissociator (''Ds''), in the color formation of maize see ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terminal Deoxynucleotidyl Transferase
Terminal deoxynucleotidyl transferase (TdT), also known as DNA nucleotidylexotransferase (DNTT) or terminal transferase, is a specialized DNA polymerase expressed in immature, pre-B, pre-T lymphoid cells, and acute lymphoblastic leukemia/lymphoma cells. TdT adds N-nucleotides to the V, D, and J exons of the TCR and BCR genes during antibody gene recombination, enabling the phenomenon of junctional diversity. In humans, terminal transferase is encoded by the ''DNTT'' gene. As a member of the X family of DNA polymerase enzymes, it works in conjunction with polymerase λ and polymerase μ, both of which belong to the same X family of polymerase enzymes. The diversity introduced by TdT has played an important role in the evolution of the vertebrate immune system, significantly increasing the variety of antigen receptors that a cell is equipped with to fight pathogens. Studies using TdT knockout mice have found drastic reductions (10-fold) in T-cell receptor (TCR) diversity compa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MicroRNA
MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRNAs base-pair to complementary sequences in mRNA molecules, then gene silence said mRNA molecules by one or more of the following processes: (1) cleavage of mRNA strand into two pieces, (2) destabilization of mRNA by shortening its poly(A) tail, or (3) translation of mRNA into proteins. This last method of gene silencing is the least efficient of the three, and requires the aid of ribosomes. miRNAs resemble the small interfering RNAs (siRNAs) of the RNA interference (RNAi) pathway, except miRNAs derive from regions of RNA transcripts that fold back on themselves to form short hairpins, whereas siRNAs derive from longer regions of double-stranded RNA. The human genome may encode over 1900 miRNAs, although more recent analysis sugges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Small Interfering RNA
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA at first non-coding RNA molecules, typically 20-24 (normally 21) base pairs in length, similar to MicroRNA, miRNA, and operating within the RNA interference (RNAi) pathway. It interferes with the gene expression, expression of specific genes with complementary nucleotide sequences by degrading mRNA after transcription, preventing translation (biology), translation. Text was copied from this source, which is available under Creative Commons Attribution 4.0 International License Structure Naturally occurring siRNAs have a well-defined structure that is a short (usually 20 to 24-base pair, bp) double-stranded RNA (dsRNA) with phosphorylation, phosphorylated 5' ends and hydroxylation, hydroxylated 3' ends with two overhanging nucleotides. The Dicer enzyme catalyzes production of siRNAs from long dsRNAs and small hairpin RNAs. siRNAs can also be introduce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA-binding Protein
RNA-binding proteins (often abbreviated as RBPs) are proteins that bind to the double or single stranded RNA in cells and participate in forming ribonucleoprotein complexes. RBPs contain various structural motifs, such as RNA recognition motif (RRM), dsRNA binding domain, zinc finger and others. They are cytoplasmic and nuclear proteins. However, since most mature RNA is exported from the nucleus relatively quickly, most RBPs in the nucleus exist as complexes of protein and pre-mRNA called heterogeneous ribonucleoprotein particles (hnRNPs). RBPs have crucial roles in various cellular processes such as: cellular function, transport and localization. They especially play a major role in post-transcriptional control of RNAs, such as: splicing, polyadenylation, mRNA stabilization, mRNA localization and translation. Eukaryotic cells express diverse RBPs with unique RNA-binding activity and protein–protein interaction. According to the Eukaryotic RBP Database (EuRBPDB), there ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SnRNP
snRNPs (pronounced "snurps"), or small nuclear ribonucleoproteins, are RNA-protein complexes that combine with unmodified pre-mRNA and various other proteins to form a spliceosome, a large RNA-protein molecular complex upon which splicing of pre-mRNA occurs. The action of snRNPs is essential to the removal of introns from pre-mRNA, a critical aspect of post-transcriptional modification of RNA, occurring only in the nucleus of eukaryotic cells. Additionally, '' U7 snRNP'' is not involved in splicing at all, as U7 snRNP is responsible for processing the 3′ stem-loop of histone pre-mRNA. The two essential components of snRNPs are protein molecules and RNA. The RNA found within each snRNP particle is known as ''small nuclear RNA'', or snRNA, and is usually about 150 nucleotides in length. The snRNA component of the snRNP gives specificity to individual introns by " recognizing" the sequences of critical splicing signals at the 5' and 3' ends and branch site of introns. The snRN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hnrnp
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are complexes of RNA and protein present in the cell nucleus during gene transcription and subsequent post-transcriptional modification of the newly synthesized RNA (pre-mRNA). The presence of the proteins bound to a pre-mRNA molecule serves as a signal that the pre-mRNA is not yet fully processed and therefore not ready for export to the cytoplasm. Since most mature RNA is exported from the nucleus relatively quickly, most RNA-binding protein in the nucleus exist as heterogeneous ribonucleoprotein particles. After splicing has occurred, the proteins remain bound to spliced introns and target them for degradation. hnRNPs are also integral to the 40s subunit of the ribosome and therefore important for the translation of mRNA in the cytoplasm. However, hnRNPs also have their own nuclear localization sequences (NLS) and are therefore found mainly in the nucleus. Though it is known that a few hnRNPs shuttle between the cytoplasm and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribonucleoprotein
Nucleoproteins are proteins conjugated with nucleic acids (either DNA or RNA). Typical nucleoproteins include ribosomes, nucleosomes and viral nucleocapsid proteins. Structures Nucleoproteins tend to be positively charged, facilitating interaction with the negatively charged nucleic acid chains. The tertiary structures and biological functions of many nucleoproteins are understood.Graeme K. Hunter G. K. (2000): Vital Forces. The discovery of the molecular basis of life. Academic Press, London 2000, . Important techniques for determining the structures of nucleoproteins include X-ray diffraction, nuclear magnetic resonance and cryo-electron microscopy. Viruses Virus genomes (either DNA or RNA) are extremely tightly packed into the viral capsid. Many viruses are therefore little more than an organised collection of nucleoproteins with their binding sites pointing inwards. Structurally characterised viral nucleoproteins include influenza, rabies, Ebola, Bunyamwera, Schmal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SR Protein
SR proteins are a conserved family of proteins involved in RNA splicing. SR proteins are named because they contain a protein domain with long repeats of serine and arginine amino acid residues, whose standard abbreviations are "S" and "R" respectively. SR proteins are ~200-600 amino acids in length and composed of two domains, the RNA recognition motif (RRM) region and the RS domain. SR proteins are more commonly found in the nucleus than the cytoplasm, but several SR proteins are known to shuttle between the nucleus and the cytoplasm. SR proteins were discovered in the 1990s in Northern Ireland, Belfast and in amphibian oocytes, and later in humans. In general, metazoans appear to have SR proteins and unicellular organisms lack SR proteins. SR proteins are important in constitutive and alternative pre-mRNA splicing, mRNA export, genome stabilization, nonsense-mediated decay, and translation. SR proteins alternatively splice pre-mRNA by preferentially selecting different spli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas2
Cas2 is a protein associated with CRISPR that is involved with spacer acquisition. Representative cas2 proteins have been characterized as endonucleases that cleave single-stranded RNAs preferentially within U-rich regions, or as metal-dependent endonucleases targeting double-stranded (ds)DNA References Enzymes {{enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas1
CRISPR-associated protein 1 (cas1) is one of the two universally conserved proteins found in the CRISPR prokaryotic immune defense system. Cas1 is a metal-dependent DNA-specific endonuclease that produces double-stranded DNA fragments. Cas1 forms a stable complex with the other universally conserved CRISPR-associated protein, cas2, which is essential to spacer acquisition for CRISPR systems. In July 2017, researchers led by Jennifer Doudna from the University of California at Berkeley, in Berkeley, California, using electron microscopy and X-ray crystallography, at the Advanced Light Source at Lawrence Berkeley National Laboratory, the Stanford Linear Accelerator Center, and the HHMI electron microscope facility at UC Berkeley, discovered how Cas1-Cas2, the proteins responsible for the ability of the CRISPR immune system (CRISPR means: clustered regularly interspaced short palindromic repeats) in bacteria to adapt to new viral infections A viral disease (or viral infection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAG2
Recombination activating gene 2 protein (also known as RAG-2) is a lymphocyte-specific protein encoded by RAG2 gene on human chromosome 11. Together with RAG1 protein, RAG2 forms a V(D)J recombinase, a protein complex required for the process of V(D)J recombination during which the variable regions of immunoglobulin and T cell receptor genes are assembled in developing B and T lymphocytes. Therefore, RAG2 is essential for generation of mature B and T lymphocytes. Structure RAG2 is a 527-amino acid long protein. Its N-terminal part is thought to form a six-bladed propeller in the active core. RAG2 is conserved among all species that carry out V(D)J recombination and its expression pattern correlates precisely with V(D)J recombinase activity. RAG2 is expressed in immature lymphoid cells. While amount of RAG1 is constant during the cell cycle, RAG2 accumulates mainly in G0 and G1 phase of cell cycle and it undergoes rapid degradation when the cell enters S phase. This serves as an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
