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Sequences of the nucleocapsid genes from two strains of avian infectious bronchitis virus
Abstract:
cDNAs prepared from viral genomic RNA purified from two strains of infectious bronchitis virus (IBV) (Beaudette and M41) have been cloned into pBR322. Three of these clones, which contain the complete sequences of mRNA A for both strains, except for the leader sequences which are only present on the subgenomic messenger RNAs, have been sequenced using the dideoxy method. The sequences are similar for both strains, each containing a single long open reading frame of 1227 bases which predicts a polypeptide of molecular weight approximately 45 000. The genome position and size of this predicted polypeptide are consistent with it being the gene for the nucleocapsid protein. The amino acid sequence shows considerable homology with those of the nucleocapsids of murine hepatitis virus strains A59 and JHM. The major difference between the sequences determined for the two IBV strains is that the 3' non-coding region of the Beaudette strain contains a 184 base segment which is not present in the M41 strain.
Insights
Researchers sequenced infectious bronchitis virus (IBV) mRNA A from two strains, identifying the nucleocapsid protein gene. Sequence analysis revealed significant homology and a unique segment in one IBV strain.
Area of Science:
- Virology
- Molecular Biology
- Genomics
Background:
- Infectious Bronchitis Virus (IBV) is a significant pathogen in poultry.
- Understanding IBV genome organization is crucial for developing control strategies.
Purpose of the Study:
- To clone and sequence mRNA A from two IBV strains (Beaudette and M41).
- To identify the gene encoding the nucleocapsid protein and analyze its sequence characteristics.
Main Methods:
- Cloning of viral genomic RNA cDNAs into pBR322.
- Dideoxy sequencing of complete mRNA A sequences.
- Bioinformatic analysis of open reading frames and amino acid sequences.
Main Results:
- Complete mRNA A sequences were obtained for both IBV strains.
- A single open reading frame of 1227 bases was identified, predicting a 45 kDa nucleocapsid protein.
- High amino acid homology was observed with murine hepatitis virus nucleocapsids.
- A 184-base segment was found in the 3' non-coding region of the Beaudette strain, absent in M41.
Conclusions:
- The sequenced gene likely encodes the IBV nucleocapsid protein.
- Sequence comparison highlights conserved regions and strain-specific variations in IBV.
- The findings contribute to the molecular understanding of IBV and related coronaviruses.