Localization of multiple TMV encapsidation initiation sites on rbcL gene transcripts.
TMV capsid protein reacts with and encapsidates many of the chloroplast DNA transcripts both in vivo and in vitro to form pseudovirions. We report on the encapsidation initiation reaction with one of the major RNA species found in in vivo formed pseudovirions, the mRNA for the chloroplast-encoded large subunit of ribulose bisphosphate carboxylase/oxygenase (rbcL). This mRNA is found to contain at least three sites which are independently capable of reacting with capsid protein oligomers to initiate encapsidation. All three sites react with capsid protein less efficiently in vitro than does the functional viral RNA encapsidation initiation site (ei). The 5' portion of the region that contains the most reactive rbcL site, ei-3, shows significant nucleotide sequence homology with the encapsidation initiation sites of the U1 and Cc strains of TMV and it can assume a folding structure that resembles that postulated for the Cc strain site. A site that acts as a block to rod elongation is present in transcripts from the region just 3' to the segment from which the rbcL mRNA is transcribed, probably close to, or at the transcription termination signal.
Atreya
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CD
Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202.
Siegel
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A
D001483:Base Sequence; D002213:Capsid / Q000378:metabolism*; D002736:Chloroplasts; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014027:Tobacco Mosaic Virus / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D012367:RNA, Viral; D012273:Ribulose-Bisphosphate Carboxylase