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Primary structure and gene organization of the middle-component RNA of cowpea mosaic virus
Abstract:
Middle component RNA (M RNA) of cowpea mosaic virus (CPMV) was transcribed into cDNA and double-stranded cDNA was inserted into the EcoRI site of plasmid pBRH2. The nucleotide sequence of inserts was determined, after subcloning in bacteriophages M13mp7, M13mp8 or M13mp9, by the dideoxy chain termination method. The complete sequence of CPMV M RNA, up to the poly(A) tail, is 3481 nucleotides long. The sequence contains a long open reading frame starting at nucleotide 161 from the 5' terminus and continuing to 180 nucleotides from the 3' terminus. The sequence does not contain a polyadenylation signal for the poly(A) tail at the 3' end of CPMV RNA. The initiation site at position 161 together with AUG codons in the same reading frame at positions 512 and/or 524 account for the two large colinear precursor polypeptides translated in vitro from M RNA. The amino acid sequence deduced from the nucleotide sequence suggests that both precursor polypeptides are proteolytically cleaved at glutaminyl-methionine and glutaminyl-glycine, respectively, to produce the two viral capsid proteins.
Insights
The complete nucleotide sequence of cowpea mosaic virus (CPMV) middle component RNA (M RNA) was determined. This sequence reveals the genetic basis for two precursor polypeptides, which are proteolytically cleaved to form viral capsid proteins.
Area of Science:
- Molecular Biology
- Virology
- Genomics
Background:
- Cowpea mosaic virus (CPMV) is a significant plant pathogen.
- Understanding the genetic makeup of CPMV is crucial for controlling its spread and impact.
Purpose of the Study:
- To determine the complete nucleotide sequence of the CPMV M RNA.
- To identify the genetic elements responsible for viral protein synthesis.
Main Methods:
- RNA transcription into cDNA.
- Insertion of cDNA into plasmid pBRH2.
- Nucleotide sequencing using the dideoxy chain termination method.
Main Results:
- The complete CPMV M RNA sequence is 3481 nucleotides long.
- A long open reading frame was identified, starting at nucleotide 161.
- The sequence analysis predicted two large colinear precursor polypeptides.
Conclusions:
- The M RNA sequence provides insights into the translation of CPMV proteins.
- Proteolytic cleavage sites (glutaminyl-methionine and glutaminyl-glycine) were identified.
- The deduced amino acid sequence explains the formation of viral capsid proteins.