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There are diverse structures of RNA base quadruplexes. Four consecutive guanine residues can form a quadruplex in RNA by Hoogsteen hydrogen bonds to form a “Hoogsteen ring” (See Figure). [12] G-C and A-U pairs can also form base quadruplex with a combination of Watson-Crick pairing and noncanonical pairing in the minor groove. [17]
Chemical structures for Watson–Crick and Hoogsteen A•T and G•C+ base pairs. The Hoogsteen geometry can be achieved by purine rotation around the glycosidic bond (χ) and base-flipping (θ), affecting simultaneously C8 and C1 ′ (yellow). [1] A Hoogsteen base pair is a variation of base-pairing in nucleic acids such as the A
A stem-loop occurs when two regions of the same nucleic acid strand, usually complementary in nucleotide sequence, base-pair to form a double helix that ends in a loop of unpaired nucleotides. Stem-loops are most commonly found in RNA, and are a key building block of many RNA secondary structures.
A tetraloop is a four-base pairs hairpin RNA structure. There are three common families of tetraloop in ribosomal RNA: UNCG, GNRA, and CUUG (N is one of the four nucleotides and R is a purine). UNCG is the most stable tetraloop. [9] Pseudoknot is an RNA secondary structure first identified in turnip yellow mosaic virus. [10] It is minimally ...
Post-transcriptional expression levels of many genes can be controlled by RNA interference, in which miRNAs, specific short RNA molecules, pair with mRNA regions and target them for degradation. [46] This antisense-based process involves steps that first process the RNA so that it can base-pair with a region of its
It is, however, not so simple for single stranded folded functional RNA molecules. Several algorithms have been implemented in software tools for the automated detection of base pairs in RNA structures solved by X-ray crystallography, NMR or other methods. Essentially the programs detect hydrogen bonds between two bases, and ensure their (near ...
The genomic RNA of retroviruses is linked non-covalently to the dimer linkage structure (DLS), a non-coding region in the 5' UTR. For the kissing loop interaction to occur, there is a triple interaction that involves a 5'-flanking purine and 2 centralized bases in the complementary strand.
Each of the base pairs in a typical double-helix DNA comprises a purine and a pyrimidine: either an A paired with a T or a C paired with a G. These purine-pyrimidine pairs, which are called base complements, connect the two strands of the helix and are often compared to the rungs of a ladder. Only pairing purine with pyrimidine ensures a ...