Autogenous regulation of the Escherichia coli ksgA gene at the level of translation

Abstract

Various plasmids that contain the Escherichia coli ksgA gene, which encodes a 16S rRNA adenosine dimethyltransferase (methylase), were constructed. In one of these plasmids, the DNA encoding the N-terminal part of the methylase was fused to the lacZ gene, and in another construct, the ksgA gene contained a deletion which resulted in a truncated version of the methylase. When a cell contained one plasmid directing the synthesis of the intact, active methylase and another plasmid encoding the methylase-4-galactosidase protein, production of the latter product became strongly reduced. Likewise, synthesis of the truncated version of the methylase was diminished when the cell at the same time contained a plasmid producing the complete enzyme. These results were partly substantiated by in vitro experiments with a coupled transcription-translation assay system. By using a recently developed gel electrophoresis system for measuring protein-nucleic acid interactions, a specific binding of the ksgA methylase with its own mRNA could be established. Our results demonstrate that the expression of the ksgA gene can be, at least partly, autogenously controlled at the level of translation.

Crystal Structure of KsgA, a Universally Conserved rRNA Adenine Dimethyltransferase in Escherichia coli

“…20 Although 16 S rRNA contains the modified adenosine bases, 16 S rRNA is not a substrate for KsgA. 15,21 KsgA will bind to a small fragment of rRNA containing the target adenosine bases, 22 but will not methylate free 16 S. Partially formed 30 S subunits, consisting of 16 S rRNA plus a subset of ribosomal proteins, seem to be the minimal substrate, 21 and the fully formed 30 S subunit can serve as efficient substrate. 23 Dim1 is the yeast ortholog of KsgA.…”

Structural Insights into Methyltransferase KsgA Function in 30S Ribosomal Subunit Biogenesis

“…Although KsgA has been reported to bind to a fragment of 16 S rRNA. including the modified nucleotides, it does not modify naked 16 S rRNA (10,16,18). More specifically, KsgA requires the 30S subunit to be in a translationally inactive conformation, which can be obtained in vitro by magnesium depletion (17).…”

Translational autoregulation of the sgm gene from Micromonospora zionensis

“…The ermC gene confers resistance to erythromycin in grampositive bacteria, and in addition to translational attenuation, this gene is autoregulated (4,13). In addition, the ksgA gene, a 16S rRNA-modifying enzyme, is autoregulated at the level of translation (43). The autoregulatory mechanisms in these examples are based on similarity between the mRNA (in sequence or secondary structure) and the target site of the respective protein.…”