Bipartite signal for read-through suppression in murine leukemia virus mRNA: an eight-nucleotide purine-rich sequence immediately downstream of the gag termination codon followed by an RNA pseudoknot.
The pol gene of murine leukemia virus and other mammalian type C retroviruses is expressed by read-through suppression of an in-frame UAG codon which separates the gag and pol coding regions. In this study, we have analyzed the sequence requirements for read-through suppression by placing different portions of wild-type and mutant viral sequences from the gag-pol junction between reporter genes and testing transcripts of these constructs for suppression in reticulocyte lysates. We find that the read-through signal is contained within the first 57 nucleotides on the 3' side of the UAG codon. Our results indicate that the identities of six conserved bases in the eight-nucleotide, purine-rich sequence immediately downstream of the UAG codon are critical for suppression, as is the existence of a pseudoknot structure spanning the next 49 nucleotides. Thus, read-through suppression depends on a complex, bipartite signal in the mRNA.
Feng
Y X
YX
Laboratory of Molecular Virology and Carcinogenesis, NCI-Frederick Cancer Research and Development Center, Maryland 21702.
Yuan
H
H
Rein
A
A
Levin
J G
JG
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D015685:Fusion Proteins, gag-pol / Q000235:genetics; D015750:Genes, gag; D015751:Genes, pol; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D012156:Reticulocytes / Q000378:metabolism; D015398:Signal Transduction; D013489:Suppression, Genetic; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
D003062:Codon; D015685:Fusion Proteins, gag-pol; D012333:RNA, Messenger; D012367:RNA, Viral