We investigated the spontaneous ribosome readthrough, virtually unexplored in genes encoding secreted proteins, over coagulation F9 nonsense mutations. Expression of recombinant factor IX (FIX) in eukaryotic cells demonstrated appreciable levels of secreted FIX molecules for the mutations p.R162(5 ± 0.3% of rFIX-wt antigen levels), p.R294(3.1 ± 1.1%) and p.R298(2.5 ± 0.7%), but not for the p.L103. Western blotting revealed a large proportion of truncated molecules, which correlated with small amounts of full-length FIX (rFIX-162, ∼0.5%; rFIX-294; and rFIX-298, ∼0.2%). Western blotting of plasma from FIX deficient (Hemophilia B) patients revealed traces of full-length FIX for the p.R294 and p.R298 mutations, but not for the p.L103 mutation that triggered major FIX mRNA decay. The detection of full-length proteins has clinical implication, particularly for post-therapeutic immunological complications in Hemophilia. Data in patients' plasma and in vitro, obtained in the proper protein context, support a ribosome readthrough gradient, consistent with its predicted determinants of efficiency. © 2012 Wiley Periodicals, Inc.
Ribosome readthrough accounts for secreted full-length factor IX in hemophilia B patients with nonsense mutations
PINOTTI, Mirko;CARUSO, Pierpaolo;CANELLA, Alessandro;CAMPIONI, Matteo;BERNARDI, Francesco
2012
Abstract
We investigated the spontaneous ribosome readthrough, virtually unexplored in genes encoding secreted proteins, over coagulation F9 nonsense mutations. Expression of recombinant factor IX (FIX) in eukaryotic cells demonstrated appreciable levels of secreted FIX molecules for the mutations p.R162(5 ± 0.3% of rFIX-wt antigen levels), p.R294(3.1 ± 1.1%) and p.R298(2.5 ± 0.7%), but not for the p.L103. Western blotting revealed a large proportion of truncated molecules, which correlated with small amounts of full-length FIX (rFIX-162, ∼0.5%; rFIX-294; and rFIX-298, ∼0.2%). Western blotting of plasma from FIX deficient (Hemophilia B) patients revealed traces of full-length FIX for the p.R294 and p.R298 mutations, but not for the p.L103 mutation that triggered major FIX mRNA decay. The detection of full-length proteins has clinical implication, particularly for post-therapeutic immunological complications in Hemophilia. Data in patients' plasma and in vitro, obtained in the proper protein context, support a ribosome readthrough gradient, consistent with its predicted determinants of efficiency. © 2012 Wiley Periodicals, Inc.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
