Analiza sekundarne strukture u okviru sgm i kgmB mRNA

Abstract

Sgm metiltransferaza iz soja Micromonospora zionensis i KgmB metiltransferaza iz soja Streptoalloteichus tenebrarius ostvaruju rezistenciju na aminoglikozidne antibiotike metilacijom nukleotida na poziciji G1405 u okviru A mesta na 16S rRNK. Smatra se da je za autoregulaciju sgm gena odgovoran (C)CCGCCC motiv. Najverovatnije je ista sekvenca odgovorna i za autoregulaciju kgmB gena. Po kompjuterskoj predikciji, ovaj motiv, lociran u 5' netranslatirajućem regionu iRNK molekula oba gena, bi mogao učestvovati u formiranju sekundarne strukture tipa ukosnice. Kako Sgm i KgmB metiltransferaze jedna drugu autoregulišu, moguće je da prepoznaju iste cis elemente u iRNK molekulima. Eksperimenti ispitivanja strukture su, s jedne strane potvrdili prisustvo stabilne sekundarne strukture u okviru 5' netranslatirajućeg regiona iRNK molekula sgm gena, a sa druge, nisu dokazali postojanje modelovane sekundarne strukture u iRNK molekulu kgmB gena.

Sgm methyltransferase from Micromonospora zionensis and KgmB methyltransferase from Streptoalloteichus tenebrarius are resistant to aminoglycoside antibiotics as a result of their ability to specifically methylate G1405 within the bacterial 16S rRNA A-site. The (C)CGCCC motif, assumed to be a regulatory sequence responsible for the autoregulation of the sgm gene, could most likely also be responsible for the autoregulation of the kgmB gene. This sequence, found within the 5' untranslated region of both sgm and kgmB mRNAs, as indicated by in silico prediction, may be involved in the formation of a specific stem-loop structure. Sgm and KgmB are mutually down-regulated and it is likely that they share the same cis-acting elements. Structure probing experiments confirmed the existence of a stable secondary structure within the 5' UTR of the sgm mRNA, while the analysis of kgmB mRNA failed to confirm the predicted structure.