Affiliation:
1. Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117871 Moscow, Russia,1 and
2. Laboratoire de Génétique Moléculaire, Ecole Normale Supérieure, 75005 Paris, France2
Abstract
ABSTRACT
The
ssyF29
mutation, originally selected as an extragenic suppressor of a protein export defect, has been mapped within the
rpsA
gene encoding ribosomal protein S1. Here, we examine the nature of this mutation and its effect on translation. Sequencing of the
rpsA
gene from the
ssyF
mutant has revealed that, due to an IS
10
R insertion, its product lacks the last 92 residues of the wild-type S1 protein corresponding to one of the four homologous repeats of the RNA-binding domain. To investigate how this truncation affects translation, we have created two series of
Escherichia coli
strains (
rpsA
+
and
ssyF
) bearing various translation initiation regions (TIRs) fused to the chromosomal
lacZ
gene. Using a β-galactosidase assay, we show that none of these TIRs differ in activity between
ssyF
and
rpsA
+
cells, except for the
rpsA
TIR: the latter is stimulated threefold in
ssyF
cells, provided it retains at least ca. 90 nucleotides upstream of the start codon. Similarly, the activity of this TIR can be severely repressed in
trans
by excess S1, again provided it retains the same minimal upstream sequence. Thus, the
ssyF
stimulation requires the presence of the
rpsA
translational autogenous operator. As an interpretation, we propose that the
ssyF
mutation relieves the residual repression caused by normal supply of S1 (i.e., that it impairs autogenous control). Thus, the C-terminal repeat of the S1 RNA-binding domain appears to be required for autoregulation, but not for overall mRNA recognition.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference45 articles.
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5. The solution structure of the S1 RNA binding domain: a member of an ancient nucleic acid-binding fold;Bycroft M.;Cell,1997
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