In genetics, a kissing stem-loop, or kissing stem loop interaction, is formed in

ribonucleic acid Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohyd ...

(RNA) when two bases between two hairpin loops pair. These intra- and intermolecular kissing interactions are important in forming the

tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

quaternary structure Protein quaternary structure is the fourth (and highest) classification level of protein structure. Protein quaternary structure refers to the structure of proteins which are themselves composed of two or more smaller protein chains (also refe ...

of many RNAs. RNA kissing interactions, also called loop-loop pseudoknots, occur when the unpaired

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecu ...

s in one hairpin loop,

base pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both D ...

with the unpaired nucleotides in another hairpin loop. When the hairpin loops are located on separate RNA molecules, their intermolecular interaction is called a kissing complex. These interactions generally form between stem-loops. However, stable complexes have been observed containing only two intermolecular Watson–Crick base pairs.

Biological significance

RNA molecules perform their function in living cells by adopting specific and highly complex 3-dimensional structures. It is believed that recombination may be initiated by the kissing loops. Recombination is critical to successful evolution, especially in the adaptation and survival of viruses. Furthermore, the kissing complex is composed of two hairpin loops that function as a regulator of CoLE1 plasmid in the E.Coli bacteria. This regulation happens when the antisense RNA of E.Coli and RNA primer responsible for DNA replication hybridizes to form the kissing complex.

In retroviruses

Retroviruses A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptas ...

are viruses that are very similar in structure, which allows them to silently replicate inside a host, keeping it alive until the replication is completed and the host is no longer needed. The genomic RNA of retroviruses is linked non-covalently to the

dimer Dimer may refer to: * Dimer (chemistry), a chemical structure formed from two similar sub-units ** Protein dimer, a protein quaternary structure ** d-dimer * Dimer model, an item in statistical mechanics, based on ''domino tiling'' * Julius 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. This interaction transcripts in the major groove of the kissing loop dimer. The human immunodeficiency virus ( HIV) is a retrovirus that can be transmitted via the interactions of bodily fluids. There are two types of HIV viruses, human immunodeficiency virus type 1 (

HIV-1 The subtypes of HIV include two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa, while HIV-2 viruses are related to viruses found in the sooty mangabey ...

) and human immunodeficiency virus type 2 (

HIV-2 The subtypes of HIV include two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa, while HIV-2 viruses are related to viruses found in the sooty mangabe ...

). From the two types of the Human Immunodeficiency Virus strain, HIV-1 is the most common strain. The RNA of the HIV-1 virus uses the kissing stem loop interaction as a means of recognition, the main step of interaction of the dimerization initiation site (DIS) to form the duplex. To study the kissing stem-loop loop interaction, It was seen that the Dimerization initiation site (DIS) complex was essential to the replication of the HIV type 1 virus in the

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

cell, and any changed to the stem loop structure diminished the dimerization interaction. Experimentally, it has been seen that, in vivo, mutating the Dimerization initiation site (DIS) obstructed the dimerization of the DIS complex.

References

External links

* {{Biomolecular structure Cis-regulatory RNA elements Retroviridae

Biological significance

In retroviruses

See also

References

Further reading

External links