Distribution of minigenes in the bacteriophage lambda chromosome

Gene. 2004 Mar 31;329:115-24. doi: 10.1016/j.gene.2003.12.031.


The bar loci in the chromosome of bacteriophage lambda inhibit phage vegetative growth in bacteria defective for peptidyl-tRNA hydrolase (Pth). Expression of the bar regions results in accumulation of peptidyl-tRNA, inhibition of protein synthesis, and arrest of mutant cell growth. These effects have been ascribed to the expression of two-codon ORFs present in translatable sequences named 'minigenes' in the lambda bar regions. To investigate the nature, frequency, and distribution of minigenes in the phage genome, we conducted a survey of their location in lambda DNA. A short-fragment random genomic DNA library was constructed for the identification of clones inhibitory of Pth-defective cells (bar-like phenotype). Three new bar-like minigenes were identified in the library but only one was on the sense strand and it had a rare initiation codon. This result contrasted with the in silico identification of over a hundred putative minigenes using an ad hoc computer program on both strands of lambda DNA. Unlike bar constructs, most of the toxic constructed clones were also toxic to wild-type bacteria, thus suggesting a different inhibition mechanism. Sequence analysis of these cloned inserts showed that they harbored minigenes, mini-ORFs, gene starts, gene ends, or combinations thereof. Our data suggest that minigene-like sequences may, at least partly, account for toxicity in wild-type cells. We propose that clustering of minigenes at gene ends may play a role in gene expression. Other minigenes identified in silico were non-toxic. It is still an open question what the in vivo function of these and toxic minigenes might be.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophage lambda / genetics*
  • Base Sequence
  • Carboxylic Ester Hydrolases / genetics
  • Chromosome Mapping / methods
  • Cloning, Molecular / methods
  • Computational Biology / methods
  • DNA, Viral / chemistry
  • DNA, Viral / genetics
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Escherichia coli / virology
  • Gene Order
  • Genes, Viral / genetics*
  • Genome, Viral*
  • Molecular Sequence Data
  • Mutation
  • Sequence Analysis, DNA


  • DNA, Viral
  • Carboxylic Ester Hydrolases
  • aminoacyl-tRNA hydrolase