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Expression of four genes of bacteriophage MB78 from contiguous open reading frames: the genomic organization as

R Sharma1, P Datta, M Chakravorty

  • 1Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi.

Virus Genes
|April 15, 2000
PubMed

Insights

Bacteriophage MB78 expresses four proteins from a single DNA fragment, utilizing overlapping genes and rare start codons. Additional genes were found on the complementary DNA strand.

Area of Science:

  • Molecular Biology
  • Genomics
  • Virology

Background:

  • Bacteriophage MB78 genome organization and gene expression are not fully understood.
  • Identification of specific DNA fragments encoding multiple proteins is crucial for understanding phage biology.

Purpose of the Study:

  • To characterize the expression of four proteins from a 3.9 kb SalI-HindIII fragment of bacteriophage MB78.
  • To investigate the genetic organization and translational mechanisms of these genes.

Main Methods:

  • DNA fragment analysis (SalI-HindIII digestion).
  • Protein molecular weight determination (apparent molecular weights: 35, 14, 21, and 16 kDa).
  • Bioinformatic analysis of open reading frames (ORFs) and codon usage.
  • Experimental evidence to support sequence analysis.

Main Results:

  • Four bacteriophage MB78 proteins (35, 14, 21, 16 kDa) are encoded by a 3.9 kb DNA fragment.
  • These proteins are likely expressed from a polycistronic mRNA without intercistronic gaps.
  • Overlapping stop and start codons and rare initiation codons suggest efficient gene expression.
  • Computer analysis revealed two additional ORFs on the complementary DNA strand within the 35 and 16 kDa ORFs.

Conclusions:

  • The 3.9 kb SalI-HindIII fragment contains a compact gene cluster in the bacteriophage MB78 genome.
  • Polycistronic expression with overlapping ORFs and unusual initiation codons optimizes gene expression.
  • The presence of oppositely oriented ORFs on the complementary strand indicates complex genomic organization.

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