PABPII, or polyadenine binding protein II, is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
involved in the assembly of the
polyadenine tail added to newly synthesized pre-
messenger RNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.
mRNA is created during the ...
(mRNA) molecules during the process of
gene transcription
Transcription is the process of copying a segment of DNA into RNA for the purpose of gene expression. Some segments of DNA are transcribed into RNA molecules that can encode proteins, called messenger RNA (mRNA). Other segments of DNA are transc ...
. It is a regulatory protein that controls the rate at which
polyadenine polymerase
In enzymology, a polynucleotide adenylyltransferase () is an enzyme that catalyzes the chemical reaction
:ATP + RNA-3'OH \rightleftharpoons pyrophosphate + RNApA-3'OH
Thus, the two substrates of this enzyme are ATP and RNA, whereas its two pro ...
(PAP) adds
adenine
Adenine (, ) (nucleoside#List of nucleosides and corresponding nucleobases, symbol A or Ade) is a purine nucleotide base that is found in DNA, RNA, and Adenosine triphosphate, ATP. Usually a white crystalline subtance. The shape of adenine is ...
nucleotide
Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
s to the
3' end of the growing tail within the nucleus of the cell. In the absence of PABPII, PAP adds adenines slowly, typically about 12. PABPII then binds to the short polyadenine tail and induces an acceleration in the rate of addition by PAP until the tail has grown to about 200 adenines long. The mechanism by which PABPII signals the termination of the polymerization reaction once the tail has reached its required length is not clearly understood.
PABPII is distinct from the related protein
PABPI
Polyadenylate-binding protein 1 is a protein that in humans is encoded by the ''PABPC1'' gene. The protein PABP1 binds mRNA and facilitates a variety of functions such as transport into and out of the nucleus, degradation, translation, and stabil ...
in being localized to the
cell nucleus
The cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryote, eukaryotic cell (biology), cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have #Anucleated_cells, ...
rather than the
cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
.
See also
*
PABPN1
Polyadenylate-binding protein 2 (PABP-2) also known as polyadenylate-binding nuclear protein 1 (PABPN1) is a protein that in humans is encoded by the ''PABPN1'' gene
In biology, the word gene has two meanings. The Mendelian gene is a basic ...
References
* Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). ''Molecular Cell Biology.'' WH Freeman: New York, NY. 5th ed.
Gene expression
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