Key result
The U4-specific Sm core protein SSm4 is essential for U4 snRNA integrity, U4/U6 di-snRNP biogenesis, and splicing in trypanosomes.
The U4-specific Sm core protein SSm4 is essential for U4/U6 di-snRNP biogenesis and splicing in trypanosomes.
SSm4 is essential for trypanosome U4 snRNP function and viability; leaves open its utility as a selective antiparasitic target.
Spliceosomal small nuclear ribonucleoproteins (snRNPs) in trypanosomes contain either the canonical heptameric Sm ring or variant Sm cores with snRNA-specific Sm subunits. Here we show biochemically by a combination of RNase H cleavage and tandem affinity purification that the U4 snRNP contains a variant Sm heteroheptamer core in which only SmD3 is replaced by SSm4. This U4-specific, nuclear-localized Sm core protein is essential for growth and splicing. As shown by RNA interference (RNAi) knockdown, SSm4 is specifically required for the integrity of the U4 snRNA and the U4/U6 di-snRNP in trypanosomes. In addition, we demonstrate by in vitro reconstitution of Sm cores that under stringent conditions, the SSm4 protein suffices to specify the assembly of U4 Sm cores. Together, these data indicate that the assembly of the U4-specific Sm core provides an essential step in U4/U6 di-snRNP biogenesis and splicing in trypanosomes.
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Jaé et al. (2010) studied Trypanosome splicing and snRNP assembly. SSm4 RNA interference (RNAi) knockdown and in vitro reconstitution was evaluated on snRNP assembly and splicing. The U4-specific Sm core protein SSm4 is essential for U4 snRNA integrity, U4/U6 di-snRNP biogenesis, and splicing in trypanosomes.
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