GEMIN4

The product of this gene is part of a large complex localized to the cytoplasm, nucleoli, and to discrete nuclear bodies called Gemini bodies (gems). The complex functions in spliceosomal snRNP assembly in the cytoplasm, and regenerates spliceosomes required for pre-mRNA splicing in the nucleus. The encoded protein directly interacts with a DEAD box protein and several spliceosome core proteins. Alternatively spliced transcript variants have been described, but their biological validity has not been determined.

Full Name

gem nuclear organelle associated protein 4

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 triggers eviction of the SMN complex, thereby allowing binding of SNRPD3 and SNRPB to complete assembly of the core snRNP.

Biological Process

rRNA processing Source: ProtInc
Spliceosomal snRNP assembly Source: UniProtKB

Cellular Location

Nucleus; Nucleolus; Gem; Cytoplasm. Localized in subnuclear structures next to coiled bodies, called gems, which are highly enriched in spliceosomal snRNPs and in the nucleolus.

Involvement in disease

Neurodevelopmental disorder with microcephaly, cataracts, and renal abnormalities (NEDMCR):
An autosomal recessive, severe neurodevelopmental disorder characterized by global developmental delay since infancy, microcephaly, poor or absent speech, and inability to walk or spasticity. Additional features include renal abnormalities, congenital cataracts, gastroesophageal reflux disease, seizures with onset in infancy or childhood, hyporeflexia, and non-specific white matter abnormalities on brain imaging.