Sad1 counteracts Brr2-mediated dissociation of U4/U6.U5 in tri-snRNP homeostasis.
The yeast Sad1 protein was previously identified in a screen for factors involved in the assembly of the U4/U6 di-snRNP particle. Sad1 is required for pre-mRNA splicing both in vivo and in vitro, and its human orthologue has been shown to associate with U4/U6.U5 tri-snRNP. We show here that Sad1 ... plays a role in maintaining a functional form of the tri-snRNP by promoting the association of U5 snRNP with U4/U6 di-snRNP. In the absence of Sad1, the U4/U6.U5 tri-snRNP dissociates into U5 and U4/U6 upon ATP hydrolysis and cannot bind to the spliceosome. The separated U4/U6 and U5 can reassociate upon incubation more favorably in the absence of ATP and in the presence of Sad1. Brr2 is responsible for mediating ATP-dependent dissociation of the tri-snRNP. Our results demonstrate a role of Sad1 in maintaining the integrity of the tri-snRNP by counteracting Brr2-mediated dissociation of tri-snRNP and provide insights into homeostasis of the tri-snRNP.
Mesh Terms:
Adenosine Triphosphate, Cell Cycle Proteins, Checkpoint Kinase 2, Homeostasis, Protein Interaction Domains and Motifs, RNA Helicases, Ribonucleoprotein, U4-U6 Small Nuclear, Ribonucleoprotein, U5 Small Nuclear, Ribonucleoproteins, Small Nuclear, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Adenosine Triphosphate, Cell Cycle Proteins, Checkpoint Kinase 2, Homeostasis, Protein Interaction Domains and Motifs, RNA Helicases, Ribonucleoprotein, U4-U6 Small Nuclear, Ribonucleoprotein, U5 Small Nuclear, Ribonucleoproteins, Small Nuclear, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Mol. Cell. Biol.
Date: Jan. 01, 2014
PubMed ID: 24190974
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