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J Cell Sci. 2014 May 1;127(Pt 9):2029-39. doi: 10.1242/jcs.143453. Epub 2014 Feb 25.

Fam118B, a newly identified component of Cajal bodies, is required for Cajal body formation, snRNP biogenesis and cell viability.

Author information

1
State Key Laboratory for Biocontrol and Key Laboratory of Gene Engineering of Ministry of Education, Sun Yat-Sen University-Baylor College of Medicine Joint Research Center on Biomedical Sciences, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.

Abstract

Cajal bodies are specialized and dynamic compartments in the nucleus that are involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs). Because of the dynamic and varied roles of Cajal bodies, it is of great interest to identify the components of Cajal bodies to better understand their functions. We performed a genome-wide screen to identify proteins that colocalize with coilin, the marker protein of Cajal bodies. In this study, we identified and characterized Fam118B as a newly discovered component of Cajal bodies. Fam118B is widely expressed in a variety of cell lines derived from various origins. Overexpression of Fam118B changes the canonical morphology of Cajal bodies, whereas depletion of Fam118B disrupts the localization of components of Cajal bodies, including coilin, the survival of motor neuron protein (SMN) and the Sm protein D1 (SmD1, also known as SNRPD1). Moreover, depletion of Fam118B reduces splicing capacity and inhibits cell proliferation. In addition, Fam118B associates with coilin and SMN proteins. Fam118B depletion reduces symmetric dimethylarginine modification of SmD1, which in turn diminishes the binding of SMN to this Sm protein. Taken together, these data indicate that Fam118B, by regulating SmD1 symmetric dimethylarginine modification, plays an important role in Cajal body formation, snRNP biogenesis and cell viability.

KEYWORDS:

Cajal body; Coilin; Fam118B; SMN; Symmetric dimethylarginine

PMID:
24569877
PMCID:
PMC4004977
DOI:
10.1242/jcs.143453
[Indexed for MEDLINE]
Free PMC Article
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