Ribonucleotide-diphosphate reductase subunit M2 B is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that in humans is encoded by the ''RRM2B''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. The gene encoding the RRM2B protein is located on

chromosome 8 Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 146 million base pairs (the building material of DNA) and represents between 4.5 and 5.0% of the total DNA i ...

, at position 8q23.1. The gene and its products are also known by designations MTDPS8A, MTDPS8B, and p53R2.

Function

RRM2B codes for one of two versions of the R2 subunit of

ribonucleotide reductase Ribonucleotide reductase (RNR), also known as ribonucleoside diphosphate reductase, is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides. It catalyzes this formation by removing the 2'-hydroxyl group of the ribos ...

, which generates nucleotide precursors required for DNA replication by reducing

ribonucleoside A ribonucleoside is a type of nucleoside including ribose as a component. One example of a ribonucleoside is cytidine Cytidine (symbol C or Cyd) is a nucleoside molecule that is formed when cytosine is attached to a ribose ring (also known as a ...

diphosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate () and tetrasodium pyrophosphate (), among others. Often pyrophosphate ...

s to deoxyribonucloside diphosphates. The version of R2 encoded by RRM2B is induced by

p53 p53, also known as tumor protein p53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory transcription factor protein that is often mutated in human cancers. The p53 proteins (originally thou ...

, and is required for normal DNA repair and

mtDNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in ...

synthesis in non-proliferating cells. The other form of R2 is expressed only in dividing cells.

Interactions

RRM2B has been shown to interact with Mdm2 and

Ataxia telangiectasia mutated ATM serine/threonine kinase or Ataxia-telangiectasia mutated, symbol ATM, is a serine/threonine protein kinase that is recruited and activated by DNA repair#Double-strand breaks, DNA double-strand breaks (Canonical pathway, canonical pathway), o ...

Clinical relevance

Abnormalities in this gene are one of the causes of

mitochondrial DNA depletion syndrome Mitochondrial DNA depletion syndrome (MDS or MDDS), or Alper's disease, is any of a group of autosomal recessive disorders that cause a significant drop in mitochondrial DNA in affected tissues. Symptoms can be any combination of myopathic, hep ...

(MDDS). Neonatal hypotonia,

developmental delay The term developmental delay can refer to: *Global developmental delay, an umbrella term used when children are significantly delayed in two or more areas of development *Specific developmental disorder, a classification of disorders characterize ...

encephalopathy Encephalopathy (; ) means any disorder or disease of the brain, especially chronic degenerative conditions. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of overall brain dysfunction; this syndrome ...

, with

seizures A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is writte ...

and

lactic acidosis Lactic acidosis refers to the process leading to the production of lactate by anaerobic metabolism. It increases hydrogen ion concentration tending to the state of acidemia or low pH. The result can be detected with high levels of lactate and lo ...

have been associated with mutations in this gene. MDDS is fatal, with death occurring from

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a r ...

in early childhood. It has been associated with some cases of pediatric

acute liver failure Acute liver failure is the appearance of severe complications rapidly after the first signs (such as jaundice) of liver disease, and indicates that the liver has sustained severe damage (loss of function of 80–90% of liver cells). The complicati ...

. Mutations in this gene have been shown to cause progressive external

ophthalmoplegia Ophthalmoparesis refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease. Internal ...

. Increased expression of RRM2B has been correlated with

gemcitabine Gemcitabine, sold under the brand name Gemzar, among others, is a chemotherapy medication used to treat cancers. It is used to treat testicular cancer, breast cancer, ovarian cancer, non-small cell lung cancer, pancreatic cancer, and bladder ca ...

resistance in human cholangiocarcinoma cells and may be predictive of lack of clinical benefit from gemcitabine for human cancers.

Function

Interactions

Clinical relevance

References

Further reading