HGNC Approved Gene Symbol: FAM118BCytogenetic location: 11q24.2 Genomic coordinates (GRCh38): 11:126,211,413-126,264,539 (from NCBI)▼ DescriptionFAM118B is a...
HGNC Approved Gene Symbol: FAM118B
Cytogenetic location: 11q24.2 Genomic coordinates (GRCh38): 11:126,211,413-126,264,539 (from NCBI)
FAM118B is a Cajal body component that is required for Cajal body assembly, mRNA splicing, and cell proliferation (Li et al., 2014).
▼ Cloning and Expression
By screening for proteins that colocalized with the Cajal body marker protein coilin (600272), Li et al. (2014) identified FAM118B. The deduced 351-amino acid protein has a predicted N-terminal nucleolar targeting sequence and a Sir2 (SIRT1; 604479)-like domain in its C-terminal half. Western blot analysis detected FAM118B in all cancer cell lines examined. Immunohistochemical analysis showed colocalization of FAM118B with coilin foci in nucleus. FAM118B had an apparent molecular mass of about 34 kD, similar to its predicted molecular mass.
▼ Gene Function
By coimmunoprecipitation analysis and protein pull-down assays, Li et al. (2014) found that endogenous HeLa cell FAM118B interacted with the 2 main component of Cajal bodies, coilin and SMN (SMN1; 600354). In a reciprocal experiment, SMN, but not FAM118B, coprecipitated with coilin. Knockdown of coilin resulted in diffuse redistribution of FAM118B into the nucleoplasm. Conversely, knockdown of FAM118B resulted in dispersal of coilin to tiny dots in the nucleoplasm. Knockdown of FAM118B also caused redistribution of SMN and SMD1 (SNRPD1; 601063), 1 of 7 proteins in the Sm core that binds small nucleolar RNA during small nucleolar ribonucleoprotein biogenesis. Knockdown of FAM118B reduced symmetric dimethylarginine modification of SMD1, SMB (SNRPB; 182282), and SMD3 (SNRPD3; 601062), and it reduced association of SMD1 with SMN. Depletion of FAM118B did not affect assembly of Sm protein complexes. Depletion of FAM118B reduced splicing in a synthetic reporter and in endogenous pre-mRNAs, and it reduced cell proliferation. Overexpression of FAM118B changed the morphology of Cajal bodies to a cap-like structure. Li et al. (2014) concluded that FAM118B is a Cajal body component required for normal Cajal body structure and function.
Hartz (2015) mapped the FAM118B gene to chromosome 11q24.2 based on an alignment of the FAM118B sequence (GenBank AK024756) with the genomic sequence (GRCh38).