Abstract
Cajal bodies (CBs) are nuclear organelles involved in the maturation of spliceosomal small nuclear ribonucleoproteins (snRNPs). They concentrate coilin, snRNPs and the survival motor neuron protein (SMN). Dysfunction of CB assembly occurs in spinal muscular atrophy (SMA). Here, we demonstrate that SMN is a SUMO1 target that has a small ubiquitin-related modifier (SUMO)-interacting motif (SIM)-like motif in the Tudor domain. The expression of SIM-like mutant constructs abolishes the interaction of SMN with the spliceosomal SmD1 (also known as SNRPD1), severely decreases SMN-coilin interaction and prevents CB assembly. Accordingly, the SMN SIM-like-mediated interactions are important for CB biogenesis and their dysfunction can be involved in SMA pathophysiology.
Highlights
Sumoylation is an important post-translational modification that regulates protein activity, subcellular localization, stability and protein–protein interactions (Flotho and Melchior, 2013)
We confirmed in MCF7, 293T and UR61 cells that some Cajal bodies (CBs) are enriched in SUMO1
The localization of SUMO1 in CBs was confirmed in MCF7 cells transfected with a GFPtagged wild-type human survival motor neuron protein (SMN) construct (GFP–SMNwt), used here for mutagenesis experiments
Summary
Sumoylation is an important post-translational modification that regulates protein activity, subcellular localization, stability and protein–protein interactions (Flotho and Melchior, 2013). We further show that SMN has a SIM-like motif in the Tudor domain that regulates its binding with the SmD1 protein ( known as SNRPD1) of the Sm complex and coilin.
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