Bovine coronavirus nonstructural protein 1 (p28) is an RNA binding protein that binds terminal genomic cis-replication elements.
Nonstructural protein 1 (nsp1), a 28-kDa protein in the bovine coronavirus (BCoV) and closely related mouse hepatitis coronavirus, is the first protein cleaved from the open reading frame 1 (ORF 1) polyprotein product of genome translation. Recently, a 30-nucleotide (nt) cis-replication stem-loop VI (SLVI) has been mapped at nt 101 to 130 within a 288-nt 5'-terminal segment of the 738-nt nsp1 cistron in a BCoV defective interfering (DI) RNA. Since a similar nsp1 coding region appears in all characterized groups 1 and 2 coronavirus DI RNAs and must be translated in cis for BCoV DI RNA replication, we hypothesized that nsp1 might regulate ORF 1 expression by binding this intra-nsp1 cistronic element. Here, we (i) establish by mutation analysis that the 72-nt intracistronic SLV immediately upstream of SLVI is also a DI RNA cis-replication signal, (ii) show by gel shift and UV-cross-linking analyses that cellular proteins of approximately 60 and 100 kDa, but not viral proteins, bind SLV and SLVI, (SLV-VI) and (iii) demonstrate by gel shift analysis that nsp1 purified from Escherichia coli does not bind SLV-VI but does bind three 5' untranslated region (UTR)- and one 3' UTR-located cis-replication SLs. Notably, nsp1 specifically binds SLIII and its flanking sequences in the 5' UTR with approximately 2.5 muM affinity. Additionally, under conditions enabling expression of nsp1 from DI RNA-encoded subgenomic mRNA, DI RNA levels were greatly reduced, but there was only a slight transient reduction in viral RNA levels. These results together indicate that nsp1 is an RNA-binding protein that may function to regulate viral genome translation or replication but not by binding SLV-VI within its own coding region.
Gustin
Kortney M
KM
Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996-0845, USA.
Guan
Bo-Jhih
BJ
Dziduszko
Agnieszka
A
Brian
David A
DA
D020413:3' Untranslated Regions / Q000235:genetics; D020121:5' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D045744:Cell Line, Tumor; D017938:Coronavirus, Bovine / Q000235:genetics* / Q000502:physiology; D015967:Gene Expression Regulation, Viral; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012367:RNA, Viral / Q000096:biosynthesis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics*; D017423:Sequence Analysis, RNA; D013379:Substrate Specificity; D017361:Viral Nonstructural Proteins / Q000235:genetics*; D014779:Virus Replication
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D017361:Viral Nonstructural Proteins; C087633:nonstructural protein, coronavirus