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A new coronavirus has been implicated as the causative agent of severe acute respiratory syndrome (SARS). We have used convalescent sera from several SARS patients to detect proteins in the culture supernatants from cells exposed to lavage another SARS patient. The most prominent protein in the supernatant was identified by matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) as a ϳ46-kDa species. This was found to be a novel nucleocapsid protein that matched almost exactly one predicted by an open reading frame in the recently published nucleotide sequence of the same virus isolate (>96% coverage). A second viral protein corresponding to the predicted ϳ139-kDa spike glycoprotein has also been examined by MALDI-TOF MS (42% coverage). After peptide N-glycosidase F digestion, 12 glycosylation sites in this protein were confirmed. The sugars attached to four of the sites were also identified. These results suggest that the nucleocapsid protein is a major immunogen that may be useful for early diagnostics, and that the spike glycoprotein may present a particularly attractive target for prophylactic intervention in combating SARS. Molecular & Cellular Proteomics 2: 346 -356, 2003.

We present evidence that a subset of mRNAs in the human parasitic trematode Schistosoma mansoni contain an identical 36-nucleotide spliced leader (SL) sequence at their 5' termini. The SL is derived from a 90-nucleotide nonpolyadenylylated RNA (SL RNA), presumably by trans-splicing.Neither the SL nor the SL RNA share significat sequence identity with previously described trans-spliced leaders and SL RNAs in trypanosomatid protozoans or nematodes. However, several features, such as predicted secondary structure, trimethylguanosine cap, and potential Sm binding site, suggest similarities among SL RNAs in widely divergent organisms. Our evidence also indicates that the exon 3 acceptor site of the 3-hydroxy-3-methylglutaryl-CoA reductase gene can be spliced either to the SL by trans-splicing or to an upstream exon, 2, by cis-splicing. The presence of a SL sequence in S. mansoni, a member of the phylum Platyhelminthes, suggests that transsplicing may be a common feature ofother lower invertebrates.Trans-splicing ofpre-mRNA sequences was first described in trypanosomatid protozoans (1-3). In these organisms, small nonpolyadenylylated RNAs [spliced leader (SL) RNAs] of -100 nucleotides (nt) donate a 5'-terminal 39-nt SL sequence to all pre-mRNAs to form the 5' termini of mature mRNAs. In metazoans, the description of trans-splicing has been confined to the phylum Nematoda. Trans-splicing in nematodes resembles the situation in trypanosomes as exemplified by the detection of Y-branched intermediates and the presence of consensus 5' and 3' splice sites flanking the SL and pre-mRNAs, respectively (4-6). There are, however, several notable differences. Unlike trypanosomatid protozoans, only a subset of nematode mRNAs (10-15%) mature via addition of a distinct 22-nt SL sequence (7). In addition, processing of nematode mRNA includes both cis-and trans-splicing (4). Analyses ofthese mRNAs and corresponding genomic clones have suggested that only the first exon serves as an acceptor for the 22-nt SL sequence (8).The discovery of trans-splicing in nematodes raised the question of the prevalence of this reaction in other metazoans. Nucleotide sequence analysis of SL genes in different genera of nematodes has revealed perfectly conserved copies of the 22-nt SL sequence (7, 9, 10). The nematode SL, however, does not hybridize to RNA from other metazoans such as Schistosoma mansoni, Dictyostelium, Drosophila, Xenopus, and humans (7). If these organisms process their mRNAs by trans-splicing, it is likely to involve SL sequences that are not homologous to the nematode SL.Here we present evidence that a subset of polyadenylylated transcripts in the human parasite S. mansoni, a trematode, are processed art their 5' termini by addition of a distinct 36-nt SL sequencet that shares no sequence identity with the 22-nt SL in nematodes or the 39-nt SL in trypanosomatid protozoans. Trematodes, cestodes, turbellarians, and monogeneans are grouped together into the morphologically diverse phylum Platyhelminthes and are distinctly differ...