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| - | {{:Team:DTU-Denmark/Templates/Standard_page_begin|Background}}
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| - | ==How do (trans) sRNAs work as regulators==
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| - | The key-word for sRNA mediated regulation is '''base-pairing'''. A part of the sRNA shows limited complementary to the mRNA of the gene it regulates and the sRNA can thus base-pair with the mRNA. The region of base-pairing is typically only 6-20 nucleotides, and often it is only a subset of these nucleotides which seems to be critical for regulation<span class="superscript">[[#References|[2]]]</span><span class="superscript">[[#References|[3]]]</span>. This (often imperfect) base-pairing between the sRNA and target mRNA leads to changes in mRNA translation or stability - or both, and thereby influences the target gene expression<span class="superscript">[[#References|[1]]]</span>. sRNAs can be both activators and repressors for gene expression depending on what part of the mRNA molecule they base-pair with.
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| - | [[File:DTU1_sRNA_activator_repressor.png|665px|thumb|center|Overview of the mechanisms for repressing and activating trans-encoded sRNA. The orange "circles" symbolise the ribosome. Modified from<span class="superscript">[[#References|[3]]]</span>.]]
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| - | '''Repressor sRNAs''' act negatively by binding to the 5’ UTR often near the ribosome binding site. The binding inhibits translation by impeding ribosome binding and/or target the mRNA for degradation by RNases (often RNase E). Note that the degradation entails irreversible regulation<span class="superscript">[[#References|[3]]]</span>. Some sRNAs act stoichiometrically meaning that they are co-degradated with the mRNA whereas others act catalytically and are not degraded in the reaction.
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| - | '''Activator sRNAs''' act positively through an anti-antisense mechanism where sRNA base-pairing with the target mRNA disrupt an inhibitory secondary structure sequestering the ribosome-binding site. As a result, the ribosome-binding site is liberated and free to bind ribosomes<span class="superscript">[[#References|[3]]]</span>.
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| - | <html></div><div class="whitebox article"></html>
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| - | ==References==
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| - | [1] Beisel, Chase L., and Gisela Storz. “Base pairing small RNAs and their roles in global regulatory networks.” FEMS Microbiology Reviews 34, no. 5 (2010): 866-882.
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| - | [2] van Vliet, Arnoud Hm, and Brendan W Wren. “New levels of sophistication in the transcriptional landscape of bacteria.” Genome biology. 10, no. 8 (2009).
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| - | [3] Waters, Lauren S., and Gisela Storz. “Regulatory RNAs in Bacteria.” Cell 136, no. 4 (2009): 615-628.
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Latest revision as of 18:13, 21 September 2011
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