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Blood, 18 June 2009, Vol. 113, No. 25, pp. 6461-6464. Prepublished online as a Blood First Edition Paper on April 22, 2009; DOI 10.1182/blood-2009-03-207613.
THROMBOSIS AND HEMOSTASIS Rescue of coagulation factor VII function by the U1+5A snRNADepartments of 1 Biochemistry and Molecular Biology and 2 Experimental and Diagnostic Medicine, University of Ferrara, Ferrara; and 3 International Centre for Genetic Engineering and Biotechnology, Trieste, Italy Our previous studies with genomic minigenes have demonstrated that an engineered small nuclear RNA-U1 (U1+5a) partially rescued coagulation factor VII (FVII) mRNA processing impaired by the 9726+5G>A mutation. Here, to evaluate the U1+5a effects on FVII function, we devised a full-length FVII splicing-competent construct (pSCFVII-wt). This construct drove in COS-1 cells the synthesis of properly processed FVII transcripts and of secreted functional FVII (23 ± 4 ng/mL), which were virtually undetectable upon introduction of the 9726+5G>A mutation (pSCFVII-9726+5a). Cotransfection of pSCFVII-9726+5a with pU1+5a resulted in a partial rescue of FVII splicing and protein biosynthesis. The level increase in medium was dose dependent and, with a molar excess (1.5x) of pU1+5a, reached 9.5% plus or minus 3.2% (5.0 ± 2.8 ng/mL) of FVII-wt coagulant activity. These data provide the first insights into the U1-snRNA–mediated rescue of donor splice sites at protein level, thus further highlighting its therapeutic implications in bleeding disorders, which would benefit even from tiny increase of functional levels.
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