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TopicPage for mgtA 5' UTR of Escherichia coli K-12

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The mgtA 5' UTR functions as a Mg(2+)-responsive riboswitch.


In addition to the PhoP-regulated P1 promoter which crreates a 262 nt 5' UTR (4465386 to 4465647), there is a constitutive P2 promoter 83 nt upstream of P1 (Kato, 1999; Yamamoto, 2002; Minagawa, 2003). The conserved riboswitch elements are encoded entirely within the 262 nt P1-initiated 5' UTR, but of course also exists in the 345 nt 5' UTR; it is not known what effect the longer 5' UTR has on riboswitch function.

The K-12 genome coordinates for the conserved riboswitch elements are 4465439 to 4465554 and were obtained from the Rfam RF01056 database (Gardner, 2009).

The mgtA riboswitch has been primarily characterized in Salmonella, but the E. coli mgtA 5' UTR also functions as a riboswitch (Groisman, 2006; Cromie, 2006). The mgtA riboswitch causes premature termination (attenuation) of the mgtA transcript (Cromie, 2006). The mgtA riboswitch senses Mg(2+) levels and, in addition to an attenuation mechanism, targets mgtA mRNA for degradation by RNase E at high external Mg(2+) levels (Spinelli, 2008).

The divergent treR gene has four promoters; treR P3 overlaps mgtA P2 by 12 nt and treR P4 overlaps mgtA P2 by 68 nt, indicating the treR P4 and the mgtA P2 transcripts are complementary at their 5' ends, which could bind in vivo.

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