A ribonucleoprotein particle or RNP is a complex formed between RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 and RNA-binding protein

RNA-binding protein

RNA-binding proteins are proteins that bind to RNA. They bind to either double-strand or single-strand RNAs through RNA recognition motif . RNA-binding proteins may regulate the translation of RNA, and post-transcriptional events, such as RNA splicing, editing.They are cytoplasmic and nuclear...

s (RBPs). The term 'RNP foci' is also used to denote an intracellular compartment involved in processing of RNA transcripts.

RNA/RBP complexes

RBPs interact with RNA through binding motifs. Aromatic

Aromaticity

In organic chemistry, Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August...

 amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 residues in this RNA binding motif result in stacking interactions with RNA. Lysine

Lysine

Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

 residues in the helical

Helix

A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 portion of RNA binding proteins help to stabilize interactions with nucleic acids. This nucleic acid binding is a result of highly positive nature of lysine side chain

Side chain

In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called "main chain" or backbone. The placeholder R is often used as a generic placeholder for alkyl group side chains in chemical structure diagrams. To indicate other non-carbon...

s and the negative character of nucleic acid

Nucleic acid

Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...

 phosphate

Phosphate

A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 backbones. It is hypothesized that RNA sequences, called elements, in the 3'-untranslated region

Three prime untranslated region

In molecular genetics, the three prime untranslated region is a particular section of messenger RNA . It is preceeded by the coding region....

 determine the binding of RBPs, and that these RBPs determine the post-transcriptional fate of mRNAs.

RNP Granules

RNP granules are a highly diverse group of compartments. These include stress granules, processing bodies

P-bodies

Processing bodies were first described in the scientific literature by Bashkirov et. al. in 1997, in which they describe "small granules… discrete, prominent foci" as the cytoplasmic location of the mouse exoribonuclease mXrn1p. It wasn’t until 2002 that a glimpse into the nature and importance of...

, and exosomes

Exosome complex

The exosome complex is a multi-protein complex capable of degrading various types of RNA molecules...

 in somatic cells. Many RNP granules are cell type and/or species specific. For example, chromatoid bodies are found only in male germ cells, whereas transport granules have so far been found only in neurons and oocytes. RNP granules function mainly by physically separating or associating transcripts with proteins. They function in the storage, processing, degradation and transportation of their associated transcripts.

RNP granules have been shown to have particular importance in cells where post-transcriptional regulation

Post-transcriptional regulation

Post-transcriptional regulation is the control of gene expression at the RNA level, therefore between the transcription and the translation of the gene...

is of vital importance. For example, in neurons where transcripts must be transported and stored in dendrites for the formation and strengthening of connections, in oocytes/embryos where mRNAs are stored for years before being translated, and in developing sperm cells where transcription is halted before development is complete.