High impact information on SRRM1

• Upon exon ligation, association of RNPS1, UAP56, and SRm160 is destabilized [1].
• Two were identified as SRm160, a nuclear matrix-associated splicing coactivator, and hPrp8p, a core component of U5 snRNP and spliceosomes [2].
• SRm160 and a related protein SRm300 (the 300-kD nuclear matrix antigen recognized by mAb B4A11) form a complex that is required for the splicing of specific pre-mRNAs [3].
• The nuclear matrix antigen recognized by the monoclonal antibody (mAb) B1C8 is a novel serine (S) and arginine (R)-rich protein associated with splicing complexes and is named here SRm160 (SR-related matrix protein of 160 kD) [3].
• In this study, we demonstrate that DEK, together with SR proteins, associates with the SRm160 splicing coactivator in vitro [4].

Biological context of SRRM1

• Using RNA interference (RNAi) in Caenorhabditis elegans, we determined whether interactions between SRm160 and the cleavage machinery are important in a whole organism context [5].
• A second EJC protein, RNPS1, also has an ATP-dependent mobility, but SRm300, a protein that binds to SRm160 and participates with it in RNA splicing, remains immobile after ATP supplementation [6].
• Regulation of CD44 alternative splicing by SRm160 and its potential role in tumor cell invasion [7].
• Consistent with a role in 3'-end formation coupled to splicing, SRm160 was found to associate specifically with the cleavage polyadenylation specificity factor and to stimulate the 3'-end cleavage of splicing-active pre-mRNAs more efficiently than that of splicing-inactive pre-mRNAs in vitro [8].
• Reduction of SRm160 by siRNA transfection downregulates the endogenous levels of CD44 isoforms, including v5, and correlates with a decrease in tumor cell invasiveness [7].

Anatomical context of SRRM1

• SRm160 (the SR-related nuclear matrix protein of 160 kDa) functions as a splicing coactivator and 3'-end cleavage-stimulatory factor [5].
• SRm160 is highly concentrated in splicing speckles but is also present in long branched intranuclear tracks connecting splicing speckles with sites at the nuclear lamina [9].
• A 65 to 75 KD polypeptide was precipitated from monocytes by mAb H8, a 160 KD protein from monocytes by mAb U2, and two broad bands in the regions of 150 and 195 KD from granulocytes by mAb ML143 [10].
• We have studied the immunoreactivity of epidermal Merkel cells for neurofilament triplet proteins (68 KD, 70 KD, 160 KD, 200 KD), using epidermal sheets prepared from the plantar skin of human adults, which enabled us to survey large numbers of Merkel cells [11].

Associations of SRRM1 with chemical compounds

• We have recently identified a splicing "coactivator," SRm160/300, which contains SRm160 (the SR nuclear matrix protein of 160 kDa) and a 300-kDa nuclear matrix antigen [12].
• Like SRm160, the 300-kDa antigen contains domains rich in alternating S and R residues but lacks an RNA recognition motif; the protein is accordingly named "SRm300." SRm300 also contains a novel and highly conserved N-terminal domain, several unique repeated motifs rich in S, R, and proline residues, and two very long polyserine tracts [13].

Regulatory relationships of SRRM1

• These results suggest that SRm160 stimulates cleavage independently of its association with EJC components and that the cleavage-stimulatory activity of RNPS1 may be an indirect consequence of its ability to stimulate splicing [5].
• Overexpression of SRm160 stimulates inclusion of CD44 v5 when Ras is activated [7].

Other interactions of SRRM1

• Whereas SRm160 stimulated cleavage to a similar extent in the presence or absence of an active intron, stimulation of 3'-end cleavage by tethered RNPS1 is dependent on an active intron [5].
• Simultaneous RNAi of SRm160 and the cleavage factor CstF-50 (Cleavage stimulation factor 50-kDa subunit) resulted in late embryonic developmental arrest [5].
• Immunoprecipitation shows association of SRm160 with Sam68, a protein that also stimulates v5 inclusion in a Ras-dependent manner, suggesting that these two proteins interact to regulate CD44 splicing [7].
• We used a monoclonal antibody (10A8), derived from mice immunized with fractions enriched in Golgi apparatus of rat brain neurons, to isolate an intrinsic membrane sialoglycoprotein of 160 KD from rat brain [14].
• Positive staining of Lafora bodies was found with antibodies to 160 KD and 200 KD neurofilaments and to desmin [15].

References