ISSN:
1617-4623
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary To determine the role of the cI repressor in induction provoked by thymine deprivation, we have analyzed λ messenger RNA made during and the effect of cI repressor levels on thymineless induction. During thymineless induction, the l- and r-strand transcription of λ is restricted to the “early” and “delayed early” RNA. This transcriptional pattern is similar to that reported for λ mutants defective in DNA synthesis. “Late” r-strand transcription requires the addition of thymine. A decrease (to less than 10% of 0 time) in the amount of exogenous label (3H-uridine) incorporated into total RNA by the time of maximum thymineless induction was observed. Since subsequent burst sizes are not diminished by the thymine deprivation and competition experiments show that the amount of λ message RNA present is a least as great as that in heat induced λ cI857 lysogens, this decrease must involve either enlarged uridine pool sizes or decreased entry of label. The introduction into the λ lysogen of a plasmid (pKB252) carrying the λ cI gene prevents (1) the thymineless induction of λ (curing the plasmid restores thymineless induction) and, (2) the appearance of both spontaneously induced cells and free phage. Thus, thymineless induction is dependent on the level of cI repressor and spontaneous induction also appears to be the consequence of lowered repressor levels in λ lysogens.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00267412
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