Abstract
The bacteriophage λ cIII gene product has a regulatory function in the lysis-lysogeny decision following infection. The availability of a set of cIII expression mutants allowed us to establish the structure-function relationship of the cIII mRNA. We demonstrate, using defined in vitro systems, that the cIII mRNA is present in two conformations at equilibrium. Mutations that have been shown to lead to cIII overexpression were found to freeze the RNA in one conformation (structure B), and permit efficient binding to the 30 S ribosomal subunit. Mutations that have been shown to prevent cIII translation cause the mRNA to assume the alternative conformation (structure A). In this structure, the translation initiation region is occluded, thereby preventing 30 S ribosomal subunit binding. By varying the temperature or Mg2+ concentration it was possible to alter the relative proportion of the alternative structures in wild-type mRNA. We suggest that the regulation of the equilibrium between the two mRNA conformations provides a mechanism for the control of cIII gene expression.
| Original language | English |
|---|---|
| Pages (from-to) | 265-280 |
| Number of pages | 16 |
| Journal | Journal of Molecular Biology |
| Volume | 210 |
| Issue number | 2 |
| DOIs | |
| State | Published - 20 Nov 1989 |
Bibliographical note
Funding Information:We thank R. Traut for purified 30 S ribosomes and Larry Gold for providing the toeprint procedure prior to its publication. We thank Ariella Oppenheim for her help in bringing the manuscript to its present form, and Max Gottesman and Hilla Giladi for stimulating discussions. This research was supported by a Levi Eshkol grant from the National Council for Research and Development, Israel, by a joint research program with Gesellschaft fur Biotechnologische Forschung, mbH, Braunschweig, and grant ROl GM38694-OlA1 from the National Institutes of Health. This work was performed in the Irene and Davide Sala Laboratory for Molecular Genetics.