Mitochondrially encoded 12S ribosomal RNA (often abbreviated as 12S or 12S rRNA) is the

SSU rRNA Small subunit ribosomal ribonucleic acid (SSU rRNA) is the smaller of the two major RNA components of the ribosome. Associated with a number of ribosomal proteins, the SSU rRNA forms the small subunit of the ribosome. It is encoded by SSU- rDNA. ...

of the mitochondrial ribosome. In humans, 12S is encoded by the ''MT-RNR1''

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 ...

and is 959

nucleotides 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 ...

long. MT-RNR1 is one of the 37 genes contained in animal mitochondria genomes. Their 2 rRNA, 22 tRNA and 13 mRNA genes are very useful in phylogenetic studies, in particular the 12S and 16S rRNAs. The 12S rRNA is the mitochondrial homologue of the prokaryotic 16S and eukaryotic nuclear 18S ribosomal RNAs. Mutations in the MT-RNR1 gene may be associated with hearing loss. The rRNA gene also encodes a peptide MOTS-c, also known as Mitochondrial-derived peptide MOTS-c or Mitochondrial

open reading frame In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames ...

of the 12S rRNA-c.

Structure

The ''MT-RNR1'' gene is located on the p arm of the

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

at position 12 and it spans 953 base pairs.

Function

The ''MT-RNR1'' gene encodes for an rRNA responsible for regulating

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...

sensitivity and

metabolic Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the ...

homeostasis In biology, homeostasis (British English, British also homoeostasis; ) is the state of steady internal physics, physical and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning fo ...

. The protein acts as an inhibitor of the folate cycle, thereby reducing de novo purine

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

which leads to the accumulation of the de novo

purine Purine is a heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted puri ...

synthesis intermediate 5-aminoimidazole-4-carboxamide (AICAR) and the activation of the metabolic regulator 5'-AMP-activated protein kinase (AMPK). The protein also protects against age-dependent and diet-induced

resistance as well as diet-induced

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

Clinical significance

Nonsyndromic hearing loss and deafness, mitochondrial

Pathogenic mutations in the ''MT-RNR1'' gene have been found to cause late-onset Mitochondrial nonsyndromic hearing loss and deafness with predisposed aminoglycoside ototoxicities. Nonsyndromic deafness is characterized by a partial or total sensorineural hearing loss (SNHL) of variable onset and severity that is not associated with other signs and symptoms. Most forms of nonsyndromic deafness are associated with permanent

hearing loss Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spo ...

caused by damage to structures in the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

. Mutations of 1494C>T, 1555A>G, and 1095T>C in the ''MT-RNR1'' gene have been identified to cause the

Complex IV Deficiency

''MT-RNR1'' mutations have been associated with complex IV deficiency of the mitochondrial respiratory chain, also known as the

cytochrome c oxidase The enzyme cytochrome c oxidase or Complex IV (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes. It is the last enzyme in the Cellular respir ...

deficiency. Cytochrome c oxidase deficiency is a rare genetic condition that can affect multiple parts of the body, including skeletal muscles, the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

, the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

, or the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

. Common clinical manifestations include

myopathy In medicine, myopathy is a disease of the muscle in which the muscle fibers do not function properly. ''Myopathy'' means muscle disease ( Greek : myo- ''muscle'' + patheia '' -pathy'' : ''suffering''). This meaning implies that the primary defec ...

hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but it is a potential manifestation of many different dis ...

, and encephalomyopathy, lactic acidosis, and hypertrophic cardiomyopathy. A 9952G>A mutation was found in a patient with the deficiency.

References

External links

GeneReviews/NCBI/NIH/UW entry on Nonsyndromic Hearing Loss and Deafness, Mitochondrial
{{DEFAULTSORT:Mt-Rnr1 Ribosomal RNA