@article{mbs:/content/journal/jgv/10.1099/0022-1317-64-1-183, author = "Luk, Ka-Cheung and Mark, Kai-Keung", title = "Effect of Multiplicity of Infection on Transcription in Escherichia coli Cells Infected by Bacteriophage Lambda", journal= "Journal of General Virology", year = "1983", volume = "64", number = "1", pages = "183-189", doi = "https://doi.org/10.1099/0022-1317-64-1-183", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-64-1-183", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", keywords = "cro gene", keywords = "phage lambda", keywords = "gene dosage", keywords = "transcription", abstract = "SUMMARY The effect of multiplicity of infection (m.o.i.) on transcription was studied by infecting Escherichia coli with bacteriophage λcI47, λcI47O29P3 and λcI857cro27P3. DNA-RNA hybridization with γcI47 l-strand DNA, φ80immλ l-strand DNA, and λimm80 l-strand DNA were used to measure mRNA transcription from the l-strand, the l-strand of the early x-P-Q region and the late A-J-b2 region of λ bacteriophage respectively. In λcI47cro + O − P −-infected cells, transcription from the l-strand, l-strand of the early x-P-Q region and the late A-J-b2 region all decreased with increasing m.o.i. The response in the x-P-Q region was less marked than in other regions, but the pattern looked similar to that described above. When phage DNA replication was permitted, as in the case of λcI47, the response was similar to that observed in λcI47cro + O − P −-infected cells, but the level of transcription was increased two- or three-fold. In λcI857cro − P −-infected cells, the leftward transcription and the rightward transcription from the early x-P-Q region and the late A-J-b2 region all increased with increasing m.o.i., but the extent of change was less drastic than with λcro +. This result demonstrated clearly that the decreased in transcription from various regions at increasing m.o.i. of λcro + was due to the inhibitory action of the cro gene product. The results obtained with cro − strongly support the view that gene dosage is a significant controlling factor for the extent of gene expression.", }