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The two RNA loops interact through stacking interactions and through hydrogen bonding (interacting bases shown in space-filling representation). [ 1 ] In genetics, a kissing stem-loop , or kissing stem loop interaction, is formed in ribonucleic acid (RNA) when two bases between two hairpin loops pair.
DNA and RNA also contain other (non-primary) bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ψ), dihydrouridine (D), inosine (I), and 7-methylguanosine ...
In RNA, adenine-uracil pairings featuring two hydrogen bonds are equal to the adenine-thymine bond of DNA. Base stacking interactions, which align the pi bonds of the bases' aromatic rings in a favorable orientation, also promote helix formation. The stability of the loop also influences the formation of the stem-loop structure.
This allows them to act as nucleation sites for proper folding of RNA. The rare hydrogen bonds between the first guanine and fourth adenine nucleotide, extensive stacking of nucleotide bases and hydrogen bonds between 2' OH of a ribose sugar and nitrogenous bases makes the tetraloop thermodynamically stable. [10] UNCG
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]
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]
These symbols are also valid for RNA, except with U (uracil) replacing T (thymine). [1] Apart from adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytidine (m5C).
Watson-Crick base pairs in a siRNA. Hydrogen atoms are not shown. Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1' through 5'. A base is attached to the 1' position, in general, adenine (A), cytosine (C), guanine (G), or uracil (U). Adenine and guanine are purines, and cytosine and uracil are pyrimidines.