Survival motor neuron protein | |||||||||
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Identifiers | |||||||||
Symbol | SMN | ||||||||
Pfam | PF06003 | ||||||||
Pfam clan | CL0049 | ||||||||
InterPro | IPR010304 | ||||||||
SCOP2 | 1mhn / SCOPe / SUPFAM | ||||||||
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Survival of motor neuron or survival motor neuron (SMN) is a protein that in humans is encoded by the SMN1 and SMN2 genes.
SMN is found in the cytoplasm of all animal cells and also in the nuclear gems. It functions in transcriptional regulation, telomerase regeneration and cellular trafficking. [2] SMN deficiency, primarily due to mutations in SMN1, results in widespread splicing defects, especially in spinal motor neurons, and is one cause of spinal muscular atrophy. Research also showed a possible role of SMN in neuronal migration and/or differentiation. [3]
The SMN protein contains GEMIN2-binding, Tudor and YG-Box domains. [4] It localizes to both the cytoplasm and the nucleus. Within the nucleus, the protein localizes to subnuclear bodies called gems which are found near coiled bodies containing high concentrations of small ribonucleoproteins (snRNPs). This protein forms heteromeric complexes with proteins such as GEMIN2 and GEMIN4, and also interacts with several proteins known to be involved in the biogenesis of snRNPs, such as hnRNP U protein and the small nucleolar RNA binding protein. [5]
SMN complex refers to the entire multi-protein complex involved in the assembly of snRNPs, the essential components of spliceosomal machinery. [6] The complex, apart from the "proper" survival of motor neuron protein, includes at least six other proteins (gem-associated protein 2, 3, 4, 5, 6 and 7. [6]
SMN has been shown to interact with:
SMN is evolutionarily conserved including the Fungi kingdom, though only fungal organisms with a great number of introns have the Smn gene (or the splicing factor spf30 paralogue). Surprisingly, these are filamentous fungus which have mycelia, so suggesting analogy to the neuronal axons. [25]
snRNPs, or small nuclear ribonucleoproteins, are RNA-protein complexes that combine with unmodified pre-mRNA and various other proteins to form a spliceosome, a large RNA-protein molecular complex upon which splicing of pre-mRNA occurs. The action of snRNPs is essential to the removal of introns from pre-mRNA, a critical aspect of post-transcriptional modification of RNA, occurring only in the nucleus of eukaryotic cells. Additionally, U7 snRNP is not involved in splicing at all, as U7 snRNP is responsible for processing the 3′ stem-loop of histone pre-mRNA.
Gideon Dreyfuss is an American biochemist, the Isaac Norris Professor of Biochemistry and Biophysics at the University of Pennsylvania School of Medicine, and an investigator of the Howard Hughes Medical Institute. He was elected to the National Academy of Sciences in 2012.
Survival of motor neuron 1 (SMN1), also known as component of gems 1 or GEMIN1, is a gene that encodes the SMN protein in humans.
Small nuclear ribonucleoprotein Sm D1 is a protein that in humans is encoded by the SNRPD1 gene.
Small nuclear ribonucleoprotein-associated proteins B and B' is a protein that in humans is encoded by the SNRPB gene.
Small nuclear ribonucleoprotein Sm D2 is a protein that in humans is encoded by the SNRPD2 gene. It belongs to the small nuclear ribonucleoprotein core protein family, and is required for pre-mRNA splicing and small nuclear ribonucleoprotein biogenesis. Alternative splicing occurs at this locus and two transcript variants encoding the same protein have been identified.
Small nuclear ribonucleoprotein E is a protein that in humans is encoded by the SNRPE gene.
Small nuclear ribonucleoprotein Sm D3 is a protein that in humans is encoded by the SNRPD3 gene.
Gem-associated protein 2 (GEMIN2), also called survival of motor neuron protein-interacting protein 1 (SIP1), is a protein that in humans is encoded by the GEMIN2 gene.
Probable ATP-dependent RNA helicase DDX20, also known as DEAD-box helicase 20 and gem-associated protein 3 (GEMIN3), is an enzyme that in humans is encoded by the DDX20 gene.
Small nuclear ribonucleoprotein F is a protein that in humans is encoded by the SNRPF gene.
U2 small nuclear ribonucleoprotein B is a protein that in humans is encoded by the SNRPB2 gene.
Small nuclear ribonucleoprotein G is a protein that in humans is encoded by the SNRPG gene.
H/ACA ribonucleoprotein complex subunit 1 is a protein that in humans is encoded by the GAR1 gene.
Gem-associated protein 7 is a protein that in humans is encoded by the GEMIN7 gene. The gem-associated proteins are those found in the gems of Cajal bodies.
Gem-associated protein 6 is a protein that in humans is encoded by the GEMIN6 gene. The gem-associated proteins are those found in the gems of Cajal bodies.
Gem-associated protein 4 is a protein that in humans is encoded by the GEMIN4 gene.
Heterogeneous nuclear ribonucleoprotein R is a protein that in humans is encoded by the HNRNPR gene.
Gem-associated protein 5 is a protein that in humans is encoded by the GEMIN5 gene.
Survival of motor neuron 2 (SMN2) is a gene that encodes the SMN protein in humans.