טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEkaterina Verkin
SubjectInvolvement of Gene Q in the Temporal Regulation of
Bacteriophage Lambda
DepartmentDepartment of Biology
Supervisor Assistant Professor Kuhn Jonathan


Abstract

  The genome of bacteriophage l is temporally regulated and different genes are expressed and come into play at different times. A technique was developed in which a reporter gene (luciferase), that is easily measured in vivo, was inserted into precise sites within the genome of heat inducible l lysogenes. By following the production of luciferase through time it was possible to construct a temporal map of many sites within the genome. In present work I concentrated on the late genes of the pR' operon.

  By using same system, we examined the question of where does N mediated transcription from pR terminate. The results show that there is virtually no transcription of the late genes from pR even in the presence of N and the pR transcript must be terminated prior to the late gene region.

  Since Q protein is essential for viable phage production, it was of interest to examine how important is the time of expression of Q with regard to λ development. In order to test this question, the Q gene was transferred into lacZ gene of the bacterial chromosome. This strategy created a single copy of Q under the well controlled lac promoter. The results show that expressing Q at times quite different than normal has only a slight effect on time of lysis (the earlier that Q is expressed, the earlier the time of lysis) but no effect on the number of phage particles released. Thus there are no side pathways and l development proceeds normally if Q is already present before induction or expressed at times well after that which is normal. Therefore, Q is not "critical" for temporal regulation. In vivo, the half-life of Q was found to be 10 minutes at 42oC. In addition, it was discovered that monomers of the Q protein are not active in antitermination. That is, Q is acts cooperatively. Cooperativity seems to be due to the need to form dimmers or higher order multimers of the Q protein and the affinity of the monomers for each other might be quite low. Another but lesser possibility is that it takes more than one molecule of Q to cause antitermination.