Abstract
Alternative splicing of precursor mRNA is often regulated by serine/arginine-rich proteins (SR proteins) and hnRNPs, and varying their concentration in the nucleus can be a mechanism for controlling splice site selection. To understand the nucleocytoplasmic transport mechanism of splicing regulators is of key importance. SR proteins are delivered to the nucleus by transportin-SRs (TRN-SRs), importin beta-like nuclear transporters. Here we identify and characterize a non-SR protein, RNA-binding motif protein 4 (RBM4), as a novel substrate of TRN-SR2. TRN-SR2 interacts specifically with RBM4 in a Ran-sensitive manner. TRN-SR2 indeed mediates the nuclear import of a recombinant protein containing the RBM4 C-terminal domain. This domain serves as a signal for both nuclear import and export, and for nuclear speckle targeting. Finally, both in vivo and in vitro splicing analyses demonstrate that RBM4 not only modulates alternative pre-mRNA splicing but also acts antagonistically to authentic SR proteins in splice site and exon selection. Thus, a novel splicing regulator with opposite activities to SR proteins shares an identical import pathway with SR proteins to the nucleus.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Active Transport, Cell Nucleus
-
Amino Acid Sequence
-
Aspartate Carbamoyltransferase / metabolism
-
Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / metabolism
-
Cell Nucleus / metabolism
-
Dihydroorotase / metabolism
-
Exons
-
Genes, Insect
-
HeLa Cells
-
Humans
-
Molecular Sequence Data
-
Multienzyme Complexes / metabolism
-
Nerve Growth Factors
-
Nuclear Localization Signals
-
Nuclear Proteins / chemistry
-
Nuclear Proteins / genetics
-
Nuclear Proteins / metabolism*
-
Phosphoproteins / metabolism
-
Protein Structure, Tertiary
-
Proteins / metabolism
-
RNA Precursors / metabolism
-
RNA Splice Sites
-
RNA Splicing*
-
RNA-Binding Proteins / chemistry
-
RNA-Binding Proteins / metabolism*
-
Recombinant Proteins / chemistry
-
Recombinant Proteins / metabolism
-
Sequence Homology, Amino Acid
-
Serine / metabolism
-
Substrate Specificity
-
Two-Hybrid System Techniques
-
beta Karyopherins / metabolism
Substances
-
CAD trifunctional enzyme
-
MANF protein, human
-
Multienzyme Complexes
-
Nerve Growth Factors
-
Nuclear Localization Signals
-
Nuclear Proteins
-
Phosphoproteins
-
Proteins
-
RBM4 protein, human
-
RNA Precursors
-
RNA Splice Sites
-
RNA-Binding Proteins
-
Recombinant Proteins
-
beta Karyopherins
-
transportin SR2
-
Serine
-
Aspartate Carbamoyltransferase
-
Dihydroorotase
-
Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)