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Journal of Bacteriology, October 2000, p. 5872-5879, Vol. 182, No. 20
Shemyakin-Ovchinnikov Institute of Bioorganic
Chemistry, Russian Academy of Sciences, 117871 Moscow,
Russia,1 and Laboratoire de
Génétique Moléculaire, Ecole Normale
Supérieure, 75005 Paris, France2
Received 23 December 1999/Accepted 1 August 2000
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 IS10R 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
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The Last RNA-Binding Repeat of the Escherichia coli
Ribosomal Protein S1 Is Specifically Involved in Autogenous
Control
-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.
*
Corresponding author. Mailing address:
Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian
Academy of Sciences, U1. Miklukho-Maklaya 16/10, GSP-7, 117871 Moscow,
Russia. Phone/fax: (7-095)330 65 38. E-mail:
irina{at}humgen.siobc.ras.ru.
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