Nucleotide bases are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Five nucleobases—adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical. They function as the fundamental units of the genetic code, with the bases A, G, C, and T being found in DNA while A, G, C, and U are found in RNA. Thymine and uracil are distinguished by merely the presence or absence of a methyl group on the fifth carbon (C5) of these heterocyclic six-membered rings. In addition, some viruses have aminoadenine (Z) instead of adenine. It differs in having an extra amine group, creating a more stable bond to thymine.
In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. Ribonucleotides themselves are basic monomeric building blocks for RNA. Deoxyribonucleotides, formed by reducing ribonucleotides with the enzyme ribonucleotide reductase (RNR), are essential building blocks for DNA. There are several differences between DNA deoxyribonucleotides and RNA ribonucleotides. Successive nucleotides are linked together via phosphodiester bonds.
Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression.
A nucleoside triphosphate is a nucleoside containing a nitrogenous base bound to a 5-carbon sugar, with three phosphate groups bound to the sugar. They are the molecular precursors of both DNA and RNA, which are chains of nucleotides made through the processes of DNA replication and transcription. Nucleoside triphosphates also serve as a source of energy for cellular reactions and are involved in signalling pathways.
Poly (ADP-ribose) polymerase (PARP) is a family of proteins involved in a number of cellular processes such as DNA repair, genomic stability, and programmed cell death.
Transcriptional modification or co-transcriptional modification is a set of biological processes common to most eukaryotic cells by which an RNA primary transcript is chemically altered following transcription from a gene to produce a mature, functional RNA molecule that can then leave the nucleus and perform any of a variety of different functions in the cell. There are many types of post-transcriptional modifications achieved through a diverse class of molecular mechanisms.
Adenosine diphosphate ribose (ADPR) is an ester molecule formed into chains by the enzyme poly ADP ribose polymerase. ADPR is created from cyclic ADP-ribose (cADPR) by the CD38 enzyme using nicotinamide adenine dinucleotide (NAD+) as a cofactor.
Purine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms.
ADP-ribosylation is the addition of one or more ADP-ribose moieties to a protein. It is a reversible post-translational modification that is involved in many cellular processes, including cell signaling, DNA repair, gene regulation and apoptosis. Improper ADP-ribosylation has been implicated in some forms of cancer. It is also the basis for the toxicity of bacterial compounds such as cholera toxin, diphtheria toxin, and others.
In enzymology, a tRNA (guanine-N1-)-methyltransferase (EC 2.1.1.31) is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (guanine-N2-)-methyltransferase (EC 2.1.1.32) is an enzyme that catalyzes the chemical reaction
Poly [ADP-ribose] polymerase 1 (PARP-1) also known as NAD+ ADP-ribosyltransferase 1 or poly[ADP-ribose] synthase 1 is an enzyme that in humans is encoded by the PARP1 gene. It is the most abundant of the PARP family of enzymes, accounting for 90% of the NAD+ used by the family. PARP1 is mostly present in cell nucleus, but cytosolic fraction of this protein was also reported.
Tankyrase, also known as tankyrase 1, is an enzyme that in humans is encoded by the TNKS gene. It inhibits the binding of TERF1 to telomeric DNA. Tankyrase attracts substantial interest in cancer research through its interaction with AXIN1 and AXIN2, which are negative regulators of pro-oncogenic β-catenin signaling. Importantly, activity in the β-catenin destruction complex can be increased by tankyrase inhibitors and thus such inhibitors are a potential therapeutic option to reduce the growth of β-catenin-dependent cancers.
Poly [ADP-ribose] polymerase 4 is an enzyme that in humans is encoded by the PARP4 gene.
Poly [ADP-ribose] polymerase 2 is an enzyme that in humans is encoded by the PARP2 gene. It is one of the PARP family of enzymes.
Poly [ADP-ribose] polymerase 10 is an enzyme that in humans is encoded by the PARP10 gene.
DNA polymerase alpha subunit 2 is an enzyme that in humans is encoded by the POLA2 gene.
DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the POLA1 gene.
Parthanatos is a form of programmed cell death that is distinct from other cell death processes such as necrosis and apoptosis. While necrosis is caused by acute cell injury resulting in traumatic cell death and apoptosis is a highly controlled process signalled by apoptotic intracellular signals, parthanatos is caused by the accumulation of Poly(ADP ribose) (PAR) and the nuclear translocation of apoptosis-inducing factor (AIF) from mitochondria. Parthanatos is also known as PARP-1 dependent cell death. PARP-1 mediates parthanatos when it is over-activated in response to extreme genomic stress and synthesizes PAR which causes nuclear translocation of AIF. Parthanatos is involved in diseases that afflict hundreds of millions of people worldwide. Well known diseases involving parthanatos include Parkinson's disease, stroke, heart attack, and diabetes. It also has potential use as a treatment for ameliorating disease and various medical conditions such as diabetes and obesity.
Ted M. Dawson is an American neurologist and neuroscientist. He is the Leonard and Madlyn Abramson Professor in Neurodegenerative Diseases and director of the Institute for Cell Engineering at Johns Hopkins University School of Medicine. He has joint appointments in the Department of Neurology, Neuroscience and Department of Pharmacology and Molecular Sciences.
