Search results
Results from the WOW.Com Content Network
Identifying and predicting sequences which have the capacity to form quadruplexes is an important tool in further understanding their role. Generally, a simple pattern match is used for searching for possible intrastrand quadruplex forming sequences: d(G 3+ N 1-7 G 3+ N 1-7 G 3+ N 1-7 G 3+), where N is any nucleotide base (including guanine). [78]
It is possible that these sequence stretches form G-quadruplex like structures, which can suppress the expression of the related genes. The complementary cytosine rich sequences, on the other strand, may adopt another similar four stranded structure, the i-motif, stabilized by cytosine:cytosine non-canonical base pairs.
Hoogsteen pointed out that if the alternative hydrogen-bonding patterns were present in DNA, then the double helix would have to assume a quite different shape. Hoogsteen base pairs are observed in alternative structures such as the four-stranded G-quadruplex structures that form in DNA and RNA.
[1] [2] They most prominently contribute to the structure of G-quadruplexes, where their hydrogen bonding stabilizes the structure. [3] [4] Usually, there are at least two guanine tetrads in a G-quadruplex, and they often feature Hoogsteen-style hydrogen bonding. [1] Guanine tetrads are formed by sequences rich in guanine, such as GGGGC. [5]
An individual motif usually consists of only a few elements, e.g., the 'helix-turn-helix' motif which has just three. Note that, while the spatial sequence of elements may be identical in all instances of a motif, they may be encoded in any order within the underlying gene. In addition to secondary structural elements, protein structural motifs ...
G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine. [1] These structures are normally located at the telomeres (the ends of the chromosomes). The G-quadruplex can either be parallel or antiparallel depending on the loop configuration, which is a component of the structure.
Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
I-motif DNA forms from any complementary strand of G-quadruplex forming sequence. G-quadruplexes are helically shaped and found in nucleic acids that are rich in guanine. These secondary structures possess guanine tetrads formed into one of three types of strands: one, two, or four.