Overekspresija 5’ UTR mRNK sgm gena smanjuje rezistenciju na gentamicin u ćelijama Escherichia coli i Micromonospora melanosporea

Abstract

16S rRNK metilaze su eksprimirane u većini bakterija koje proizvode antibiotike da bi se zaštitile od dejstva antibiotika putem metilacije 16S rRNK na pozicijama koje su bitne za njihovo dejstvo. Gen sgm koji je odgovoran za rezistenciju na sisomicin i gentamicin u soju Micromonospora zionensis, metilu je G1405 u okviru A mesta 16S rRNA gde se nalazi i CCGCCC heksanukleotid. Isti heksanukleotid se nalazi i 14 nukleotida ispred mesta vezivanja ribozoma na sgm informacionoj RNK. Predloženi model translacione regulacije sgm gena pretpostavlja da se Sgm protein vezuje za ovaj motiv kako na 16S rRNK, tako i na 5’ netranslirajućem regionu (UTR) sopstvene informacione RNK. 5’ UTR sekvenca je overeksprimirana na sgm informacionoj RNK sa skraćenim 3’ krajem i testiran je efekat na gentamicinsku rezistenciju u ćelijama E. coli i Micromonospora melanosporea. Overekspresija ove regulatorne sekvence dovodi do smanjenja rezistencije u oba testirana soja najverovatnije zbog titracije Sgm molekula od strane 5’ UTR-a.

The 16S rRNA methylases are expressed by most of the antibiotic producing bacteria in order to protect themselves against antibiotics by methylation of 16S rRNA at positions which are crucial for their action. The sgm sisomicin-gentamicin resistance gene from Micromonospora zionensis methylates G1405 positioned in the A site of 16S rRNA, which includes a CCGCCC hexanucleotide. The same hexanucleotide is also present 14 nucleotides in front of the ribosome binding site of sgm mRNA. The model proposed for translational regulation of sgm assumes that Sgm binds to this motif, both on 16S rRNA and on the 5’ untranslated region (UTR) of its own mRNA. The 5’ UTR mRNA sequence was overexpressed on 3’-truncated sgm mRNA, and the effect on gentamicin resistance conferred by Sgm was tested in Escherichia coli and in Micromonospora melanosporea. Overexpression of the sgm mRNA regulatory region decreases the resistance to gentamicin in both E. coli and M. melanosporea. This effect is likely to be due to titration of Sgm molecules by the overexpressed 5’ UTR.