A novel SR-related protein is required for the second step of Pre-mRNA splicing.

MRC Human Genetics Unit, Western General Hospital, Crewe Rd., Edinburgh EH4 2XU, Scotland, United Kingdom.
The SR family proteins and SR-related polypeptides are important regulators of pre-mRNA splicing. A novel SR-related protein of an apparent molecular mass of 53 kDa was isolated in a gene trap screen that identifies proteins which localize to the nuclear speckles. This novel protein possesses an arginine- and serine-rich domain and was termed SRrp53 (for SR-related protein of 53 kDa). In support for a role of this novel RS-containing protein in pre-mRNA splicing, we identified the mouse ortholog of the Saccharomyces cerevisiae U1 snRNP-specific protein Luc7p and the U2AF65-related factor HCC1 as interacting proteins. In addition, SRrp53 is able to interact with some members of the SR family of proteins and with U2AF35 in a yeast two-hybrid system and in cell extracts. We show that in HeLa nuclear extracts immunodepleted of SRrp53, the second step of pre-mRNA splicing is blocked, and recombinant SRrp53 is able to restore splicing activity. SRrp53 also regulates alternative splicing in a concentration-dependent manner. Taken together, these results suggest that SRrp53 is a novel SR-related protein that has a role both in constitutive and in alternative splicing.
Mesh Terms:
Alternative Splicing, Amino Acid Sequence, Animals, Cell Nucleus, Cloning, Molecular, Cytoplasm, Hela Cells, Humans, Mice, Molecular Sequence Data, Nuclear Proteins, RNA Precursors, RNA Splice Sites, RNA, Messenger, RNA-Binding Proteins, Sequence Homology, Amino Acid, Two-Hybrid System Techniques
Mol. Cell. Biol. Apr. 01, 2005; 25(8);2969-80 [PUBMED:15798186]
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