Smn1
Domain
The Tudor domain mediates association with dimethylarginines, which are common in snRNP proteins.
Function
The SMN complex catalyzes the assembly of small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome, and thereby plays an important role in the splicing of cellular pre-mRNAs. Most spliceosomal snRNPs contain a common set of Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG that assemble in a heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP (Sm core). In the cytosol, the Sm proteins SNRPD1, SNRPD2, SNRPE, SNRPF and SNRPG are trapped in an inactive 6S pICln-Sm complex by the chaperone CLNS1A that controls the assembly of the core snRNP. To assemble core snRNPs, the SMN complex accepts the trapped 5Sm proteins from CLNS1A forming an intermediate. Binding of snRNA inside 5Sm ultimately triggers eviction of the SMN complex, thereby allowing binding of SNRPD3 and SNRPB to complete assembly of the core snRNP. Within the SMN complex, SMN1 acts as a structural backbone and together with GEMIN2 it gathers the Sm complex subunits (By similarity). Ensures the correct splicing of U12 intron-containing genes that may be important for normal motor and proprioceptive neurons development (PubMed:23063131). Also required for resolving RNA-DNA hybrids created by RNA polymerase II, that form R-loop in transcription terminal regions, an important step in proper transcription termination. May also play a role in the metabolism of small nucleolar ribonucleoprotein (snoRNPs) (By similarity).
Sequence Similarities
Belongs to the SMN family.
Tissue Specificity
Expressed in motor neurons.
Cellular localization
- Nucleus
- Gem
- Nucleus
- Cajal body
- Cytoplasm
- Cytoplasmic granule
- Perikaryon
- Cell projection
- Neuron projection
- Cell projection
- Axon
- Cytoplasm
- Myofibril
- Sarcomere
- Z line
- Colocalizes with actin and at the Z-line of skeletal muscle (PubMed:17353360). Under stress conditions colocalizes with RPP20/POP7 in punctuated cytoplasmic granules. Colocalized and redistributed with ZPR1 from the cytoplasm to nuclear gems (Gemini of coiled bodies) and Cajal bodies. Colocalizes with FMR1 in cytoplasmic granules in the soma and neurite cell processes (By similarity).
Alternative names
Smn, Smn1, Survival motor neuron protein