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Let-7 MicroRNA Precursor
The Let-7 microRNA precursor was identified from a study of developmental timing in '' C. elegans'', and was later shown to be part of a much larger class of non-coding RNAs termed microRNAs. miR-98 microRNA precursor from human is a let-7 family member. Let-7 miRNAs have now been predicted or experimentally confirmed in a wide range of species (MIPF0000002). miRNAs are initially transcribed in long transcripts (up to several hundred nucleotides) called primary miRNAs (pri-miRNAs), which are processed in the nucleus by Drosha and Pasha to hairpin structures of about 70 nucleotide. These precursors (pre-miRNAs) are exported to the cytoplasm by exportin5, where they are subsequently processed by the enzyme Dicer to a ~22 nucleotide mature miRNA. The involvement of Dicer in miRNA processing demonstrates a relationship with the phenomenon of RNA interference. Genomic Locations In human genome, the cluster ''let-7a-1/let-7f-1/let-7d'' is inside the region B at 9q22.3, with the defin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the three dimensional form of ''local segments'' of proteins. The two most common secondary structural elements are alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein folds into its three dimensional tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the amino hydrogen and carboxyl oxygen atoms in the peptide backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik Linderstrøm-Lang at Stanford in 1952. Other types of biopolymers such as nucleic acids also possess characteristic secondary structures. Types The most common seconda ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterochrony
In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a developmental process in an organism compared to its ancestors or other organisms. This leads to changes in the size, shape, characteristics and even presence of certain organs and features. It is contrasted with heterotopy, a change in spatial positioning of some process in the embryo, which can also create morphological innovation. Heterochrony can be divided into intraspecific heterochrony, variation within a species, and interspecific heterochrony, phylogenetic variation, i.e. variation of a descendant species with respect to an ancestral species. These changes all affect the start, end, rate or time span of a particular developmental process. The concept of heterochrony was introduced by Ernst Haeckel in 1875 and given its modern sense by Gavin de Beer in 1930. History The concept of heterochrony was introduced by the German zoologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDC34
''CDC34'' is a gene that in humans encodes the protein Ubiquitin-conjugating enzyme E2 R1. This protein is a member of the ubiquitin-conjugating enzyme family, which catalyzes the covalent attachment of ubiquitin to other proteins. CDC34 was originally discovered by work in baker's yeast as a gene that is essential for the cell cycle. Cdc34 in yeast targets numerous substrates - notably the cyclin-dependent kinase inhibitor Sic1 - for ubiquitin-mediated protein degradation. CDC34 is required for ubiquitin-mediated degradation of cell cycle G1 regulators, and for the initiation of DNA replication. Interactions CDC34 has been shown to interact with CSNK2B, BTRC and CDK9 Cyclin-dependent kinase 9 or CDK9 is a cyclin-dependent kinase associated with P-TEFb. Function The protein encoded by this gene is a member of the cyclin-dependent kinase (CDK) family. CDK family members are highly similar to the gene produc .... References External links * Further reading [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclin A2
Cyclin-A2 is a protein that in humans is encoded by the ''CCNA2'' gene. It is one of the two types of cyclin A: cyclin A1 is expressed during meiosis and embryogenesis while cyclin A2 is expressed in dividing somatic cells. Function Cyclin A2 belongs to the cyclin family, whose members regulate cell cycle progression by interacting with CDK kinases. Cyclin A2 is unique in that it can activate two different CDK kinases; it binds CDK2 during S phase, and CDK1 during the transition from G2 to M phase. Cyclin A2 is synthesized at the onset of S phase and localizes to the nucleus, where the cyclin A2-CDK2 complex is implicated in the initiation and progression of DNA synthesis. Phosphorylation of CDC6 and MCM4 by the cyclin A2-CDK2 complex prevents re-replication of DNA during the cell cycle. Cyclin A2 is involved in the G2/M transition but it cannot independently form a maturation promoting factor (MPF). Recent studies have shown that the cyclin A2-CDK1 complex triggers cyclin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microarray
A microarray is a multiplex lab-on-a-chip. Its purpose is to simultaneously detect the expression of thousands of genes from a sample (e.g. from a tissue). It is a two-dimensional array on a solid substrate—usually a glass slide or silicon thin-film cell—that assays (tests) large amounts of biological material using high-throughput screening miniaturized, multiplexed and parallel processing and detection methods. The concept and methodology of microarrays was first introduced and illustrated in antibody microarrays (also referred to as antibody matrix) by Tse Wen Chang in 1983 in a scientific publication and a series of patents. The " gene chip" industry started to grow significantly after the 1995 '' Science Magazine'' article by the Ron Davis and Pat Brown labs at Stanford University. With the establishment of companies, such as Affymetrix, Agilent, Applied Microarrays, Arrayjet, Illumina, and others, the technology of DNA microarrays has become the most sophistic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HMGA2
High-mobility group AT-hook 2, also known as HMGA2, is a protein that, in humans, is encoded by the ''HMGA2'' gene. Function This gene encodes a protein that belongs to the non-histone chromosomal high-mobility group (HMG) protein family. HMG proteins function as architectural factors and are essential components of the enhanceosome. This protein contains structural DNA-binding domains and may act as a transcriptional regulating factor. Identification of the deletion, amplification, and rearrangement of this gene that are associated with lipomas suggests a role in adipogenesis and mesenchymal differentiation. A gene knock-out study of the mouse counterpart demonstrated that this gene is involved in diet-induced obesity. Alternate transcriptional splice variants, encoding different isoforms, have been characterized. The expression of HMGA2 in adult tissues is commonly associated with both malignant and benign tumor formation, as well as certain characteristic cancer-promoting mu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Untranslated Region
In molecular genetics, an untranslated region (or UTR) refers to either of two sections, one on each side of a coding sequence on a strand of mRNA. If it is found on the 5' side, it is called the 5' UTR (or leader sequence), or if it is found on the 3' side, it is called the 3' UTR (or trailer sequence). mRNA is RNA that carries information from DNA to the ribosome, the site of protein synthesis (translation) within a cell. The mRNA is initially transcribed from the corresponding DNA sequence and then translated into protein. However, several regions of the mRNA are usually not translated into protein, including the 5' and 3' UTRs. Although they are called untranslated regions, and do not form the protein-coding region of the gene, uORFs located within the 5' UTR can be translated into peptides. The 5' UTR is upstream from the coding sequence. Within the 5' UTR is a sequence that is recognized by the ribosome which allows the ribosome to bind and initiate translation. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold-shock Domain
In molecular biology, the cold-shock domain (CSD) is a protein domain of about 70 amino acids which has been found in prokaryotic and eukaryotic DNA-binding proteins. Part of this domain is highly similar to the RNP-1 RNA-binding motif. When ''Escherichia coli'' is exposed to a temperature drop from 37 to 10 degrees Celsius, a 4–5 hour lag phase occurs, after which growth is resumed at a reduced rate. During the lag phase, the expression of around 13 proteins, which contain cold shock domains is increased 2–10 fold. These so-called 'cold shock' proteins are thought to help the cell to survive in temperatures lower than optimum growth temperature, by contrast with heat shock proteins, which help the cell to survive in temperatures greater than the optimum, possibly by condensation of the chromosome and organisation of the prokaryotic A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LIN28
Lin-28 homolog A is a protein that in humans is encoded by the ''LIN28'' gene. LIN28 encodes an RNA-binding protein that binds to and enhances the translation of the IGF-2 (insulin-like growth factor 2) mRNA. Lin28 binds to the let-7 pre-microRNA and blocks production of the mature let-7 microRNA in mouse embryonic stem cells. In pluripotent embryonal carcinoma cells, LIN28 is localized in the ribosomes, P-bodies and stress granules. Function Stem cell expression LIN28 is thought to regulate the self-renewal of stem cells. In '' Caenorhabditis elegans'', there is only one Lin28 gene that is expressed and in vertebrates, there are two paralogs present, Lin28a and Lin28b. In nematodes, the LIN28 homolog lin-28 is a heterochronic gene that determines the onset of early larval stages of developmental events in ''C. elegans'', by regulating the self-renewal of nematode stem cells in the skin (called seam cells) and vulva (called VPCs) during development. In mice, LIN28 is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induced Pluripotent Stem Cell
Induced pluripotent stem cells (also known as iPS cells or iPSCs) are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka's lab in Kyoto, Japan, who showed in 2006 that the introduction of four specific genes (named Myc, Oct3/4, Sox2 and Klf4), collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. He was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent." Pluripotent stem cells hold promise in the field of regenerative medicine. Because they can propagate indefinitely, as well as give rise to every other cell type in the body (such as neurons, heart, pancreatic, and liver cells), they represent a single source of cells that could be used to replace those lost to damage or disease. The most well-known type of pluripotent stem cell is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-transcriptional Regulation
Post-transcriptional regulation is the control of gene expression at the RNA level. It occurs once the RNA polymerase has been attached to the gene's promoter and is synthesizing the nucleotide sequence. Therefore, as the name indicates, it occurs between the transcription phase and the translation phase of gene expression. These controls are critical for the regulation of many genes across human tissues. It also plays a big role in cell physiology, being implicated in pathologies such as cancer and neurodegenerative diseases. Mechanism After being produced, the stability and distribution of the different transcripts is regulated (post-transcriptional regulation) by means of RNA binding protein (RBP) that control the various steps and rates controlling events such as alternative splicing, nuclear degradation ( exosome), processing, nuclear export (three alternative pathways), sequestration in P-bodies for storage or degradation and ultimately translation. These protein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stem-loop
Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions, base-pair to form a double helix that ends in an unpaired loop. The resulting structure is a key building block of many RNA secondary structures. As an important secondary structure of RNA, it can direct RNA folding, protect structural stability for messenger RNA (mRNA), provide recognition sites for RNA binding proteins, and serve as a substrate for enzymatic reactions. Formation and stability The formation of a stem-loop structure is dependent on the stability of the resulting helix and loop regions. The first prerequisite is the presence of a sequence that can fold back on itself to form a paired double helix. The stability of this helix is determined by its length, the number of mismatches or bulges it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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