Quadruplex

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This format revolutionized broadcast television operations and television production , since the only recording medium available to the TV industry until then was Motion picture film. Since most United States network broadcast delays by the television networks at the time used kinescope film that took time to develop, the networks wanted a more practical, cost-effective, and quicker way to time-shift television programming for later airing in Western time zones than the expensive and time-consuming processing and editing of film. Faced with these challenges, broadcasters sought to adapt magnetic tape recording technology already used for audio recording for use with television as well. By the television industry in the US was consuming more film stock than all Hollywood studios combined. This method is called quadrature scanning, as opposed to the helical scan transport used by later videotape formats. The tape ran at a speed of either 7. The cue track was used either as a second audio track, or for recording cue tones or time code for linear video editing.

Quadruplex

G-quadruplexes are higher-order DNA and RNA structures formed from G-rich sequences that are built around tetrads of hydrogen-bonded guanine bases. Potential quadruplex sequences have been identified in G-rich eukaryotic telomeres, and more recently in non-telomeric genomic DNA, e. The natural role and biological validation of these structures is starting to be explored, and there is particular interest in them as targets for therapeutic intervention. This survey focuses on the folding and structural features on quadruplexes formed from telomeric and non-telomeric DNA sequences, and examines fundamental aspects of topology and the emerging relationships with sequence. Emphasis is placed on information from the high-resolution methods of X-ray crystallography and NMR, and their scope and current limitations are discussed. Such information, together with biological insights, will be important for the discovery of drugs targeting quadruplexes from particular genes. Abstract G-quadruplexes are higher-order DNA and RNA structures formed from G-rich sequences that are built around tetrads of hydrogen-bonded guanine bases. Publication types Research Support, Non-U. Gov't Review. Substances Guanine DNA.

MM41, a ligand that binds selectively for a quadruplex on the BCL-2 promoter, quadruplex, is shaped with a central core and 4 side chains branching sterically out. Quadruplex to English. The average length of this single-stranded overhang, of ca.

In molecular biology, G-quadruplex secondary structures G4 are formed in nucleic acids by sequences that are rich in guanine. The placement and bonding to form G-quadruplexes is not random and serve very unusual functional purposes. The quadruplex structure is further stabilized by the presence of a cation , especially potassium , which sits in a central channel between each pair of tetrads. G-quadruplex structures can be computationally predicted from DNA or RNA sequence motifs, [11] [12] but their actual structures can be quite varied within and between the motifs, which can number over , per genome. Their activities in basic genetic processes are an active area of research in telomere, gene regulation, and functional genomics research. The identification of structures with a high guanine association became apparent in the early s, through the identification of gel-like substances associated with guanines. Interest in in vivo function of G-quadruplexes surged after large scale genome-wide analysis showed the prevalence of potential G-quadruplex pG4 -forming sequences within gene promoters of human, chimpanzee, mouse, and rat - presented in the First International G-quadruplex Meeting held in April in Louisville, Kentucky.

Sarah Burge, Gary N. Parkinson, Pascale Hazel, Alan K. G-quadruplexes are higher-order DNA and RNA structures formed from G-rich sequences that are built around tetrads of hydrogen-bonded guanine bases. Potential quadruplex sequences have been identified in G-rich eukaryotic telomeres, and more recently in non-telomeric genomic DNA, e. The natural role and biological validation of these structures is starting to be explored, and there is particular interest in them as targets for therapeutic intervention. This survey focuses on the folding and structural features on quadruplexes formed from telomeric and non-telomeric DNA sequences, and examines fundamental aspects of topology and the emerging relationships with sequence. Emphasis is placed on information from the high-resolution methods of X-ray crystallography and NMR, and their scope and current limitations are discussed. Such information, together with biological insights, will be important for the discovery of drugs targeting quadruplexes from particular genes.

Quadruplex

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The establishment of cell identity during embryonic development involves the activation of specific gene expression programmes and is underpinned by epigenetic factors including DNA methylation and histone post-translational modifications.

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Metal complexes have a number of features that make them particularly suitable as G4 DNA binders and therefore as potential drugs. Simulations have suggested a set of preferences for thymine-containing loops 53 , which are broadly in accord with the experimental observations from crystallographic and NMR studies, as outlined above, which show that T 3 loops have a marked preference for lateral loop conformations. Bibcode : PNAS.. The direct visualization of G-quadruplex structures in human cells [47] as well as the co-crystal structure of an RNA helicase bound to a G-quadruplex [48] have provided important confirmations of their relevance to cell biology. Korean English to Korean. Trends in Pharmacological Sciences. ISBN Such a quadruplex is described as tetramolecular, reflecting the requirement of four separate strands. Cancer Ther. Finally, sequences which contain four distinct runs of guanine bases can form stable quadruplex structures by themselves, and a quadruplex formed entirely from a single strand is called an intramolecular quadruplex. Reducing the number of guanines still further, to d G 3 T 4 G 3 , results in a more conventional diagonal-looped quadruplex, but with asymmetry in guanine glycosidic angles 45 , The formation and stability of G-quadruplexes is monovalent cation-dependent. Direct evidence for a G-quadruplex in a promoter region and its targeting with a small molecule to repress c- MYC transcription. Shafer R.

In molecular biology, G-quadruplex secondary structures G4 are formed in nucleic acids by sequences that are rich in guanine. The placement and bonding to form G-quadruplexes is not random and serve very unusual functional purposes. The quadruplex structure is further stabilized by the presence of a cation , especially potassium , which sits in a central channel between each pair of tetrads.

With the use of genome-wide ChIP-sequencing analyses, cell-based assays, and in vitro biochemical analyses, a connection has been made between oxidized DNA base-derived AP sites, and the formation of the G-quadruplex. Rueda M. For intramolecular quadruplexes, this means that any loop regions present must be of the propeller type, positioned to the sides of the quadruplex. The C9orf72 gene codes for the protein C9orf72 which is found throughout the brain in neuronal cytoplasm and at presynaptic terminals. Secondary School. Stefl R. Grammar Patterns. Longer sequences, which contain two contiguous runs of three or more guanine bases, where the guanine regions are separated by one or more bases, only require two such sequences to provide enough guanine bases to form a quadruplex. Analytical Chemistry. This format revolutionized broadcast television operations and television production , since the only recording medium available to the TV industry until then was Motion picture film. Influence of loop size on the stability of intramolecular DNA quadruplexes.