Team:Hong Kong HKUST/pneumosensor/module two
From 2014.igem.org
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- | <p class="first_letter_enhanced"> | + | <p class="first_letter_enhanced">In order to achieve the functionality of pneumosensor, we must have a highly specific reporting system which will only give fluorescent signal under the presence of <i>S. pneumoniae</i>. In search for the suitable gene circuit, the discovery by Prof. Morrison on the competence for genetic transformation in <i>S. pneumoniae</i> which depends on quorum-sensing system to control many competence-specific genes acting in DNA uptake, processing, and integration has provided the ideal framework for this module. (Lee and Morrison, 1999) There is a link between this quorum-sensing system and the competence-specific genes, which is an alternative σ<sup>x</sup> (ComX protein) that serves as a competence-specific global transcription modulator. (Luo and Morrison, 2003) In <i>S. pneumoniae</i>, competence (a state capable of being genetic transformed) happens transiently during the log phase growth, and is regulated by a quorum sensing system utilizing the Competence Signal Peptide (CSP). Upon stimulation by CSP, σ<sup>x</sup> will be expressed and associated with RNA polymerase apoenzyme. The resulting holoenzyme will then be guided by σ<sup>x</sup> to initiate transcription of a set of “late” genes enabling genetic transformation and other unknown functions. Characterized genes regulated by σ<sup>x</sup> were found to contain an 8 base pairs consensus sequence TACGAATA known as the Cin-Box or the Com-Box. (Piotrowski, Luo, & Morrison, 2009). Taking advantage of this competence-specific mechanism, it is now able to produce the <i>S. pneumoniae</i> sensing device of high specificity by incorporating this system into <i>E. coli</i>. <br> |
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- | + | iGEM 2014 Hong_Kong_HKUST Team has cloned σ<sup>x</sup> from <i>S. pneumoniae</i> strain NCTC7465 and characterized its ability to initiate transcription of two downstream promoters with different lengths: P<sub>celA</sub> (<a href= "http://parts.igem.org/Part:BBa_K1379000">BBa_K1379000</a>) and P<sub>comFA</sub> (<a href= "http://parts.igem.org/Part:BBa_K1379001">BBa_K1379001</a>), which have the consensus Com-Box sequence. Though much information about the promoters is readily available nowadays, its characterization of promoter activity, specificity, sequence, as well as the biomolecular mechanism can be greatly enhanced with further investigations and experiments. Hence, we were interested in reproducing this gene circuit with all the associated genes and promoters to be combined into a single transcriptional unit. Despite the suggested susceptibility to leakage and other factors that may hinder or interrupt the mechanism, researches have reported that the pathway was highly specific to certain environmental conditions and stress, suggesting minimal or no leakage in the entire process. <br> | |
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- | P | + | P<sub>celA</sub> and P<sub>comFA</sub> promoters have high specificity to σ<sup>x</sup> for activation, so genes downstream the promoters will be translated only if σ<sup>x</sup> is present. Hence, by using fluorescence protein as a reporting mechanism, this σ<sup>x</sup>, P<sub>celA</sub> and P<sub>comFA</sub> promoters system could be further utilized as a specific reporter device in <i>E. coli</i> DH10B strain that could be used by iGEM communities. |
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- | <p class="first_letter_enhanced"> | + | <p class="first_letter_enhanced">To complete the story of competence regulation mechanism from <i>S. Pneumoniae</i>, we would also like to integrate another positive factor involved in competence regulation which was later found out to be ComW. Prof. Morrison's lab released another research paper on the identification of a new component in the regulation of genetic transformation in <i>S. Pneumoniae</i>. The gene <i>comW</i> (SP0018) was found to be |
- | regulated by the quorum-sensing system and is required for a high-level of competence. Coexpression of ComW with σ<sup>x</sup> restores the accumulation of σ<sup>x</sup> and the expression of late genes as ComW contributes to the stabilization of the alternative sigma factor X against proteolysis by ClpXP and is required for full activity of σ<sup>x</sup> in directing transcription of late competence genes. | + | regulated by the quorum-sensing system and is required for a high-level of competence (Luo, Li, and Morrison, 2004). Coexpression of ComW with σ<sup>x</sup> restores the accumulation of σ<sup>x</sup> and the expression of late genes as ComW contributes to the stabilization of the alternative sigma factor X against proteolysis by ClpXP and is required for full activity of σ<sup>x</sup> in directing transcription of late competence genes (Piotrowski, Luo, and Morrison, 2009). |
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- | Based on these findings, we | + | Based on these findings, we tried to integrate this ComW into the mechanism to see whether and how the presence of ComW affects σ<sup>x</sup>. We firstly cloned out the <i>comX</i> gene expressing σ<sup>x</sup>, and <i>comW</i> genes from the genomic DNA of <i>S. pneumoniae</i> NCTC 7465 strain. We then used <a href= "http://parts.igem.org/Part:BBa_K880005">BBa_K880005</a> (consisting of constitutive promoter <a href= "http://parts.igem.org/wiki/index.php?title=Part:BBa_J23100">BBa_J23100</a> and strong RBS <a href= "http://parts.igem.org/wiki/index.php?title=Part:BBa_B0034">BBa_B0034</a>) from the BioBricks to express those genes.<br><br> |
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M. S. Lee & D. A . Morrison. (1999). Identification of a New Regulator in <i>Streptococcus pneumoniae</i> Linking Quorum Sensing to Competence for Genetic Transformation. <i>Journal of Bacteriology</i>, 181(16), 5004-5016. | M. S. Lee & D. A . Morrison. (1999). Identification of a New Regulator in <i>Streptococcus pneumoniae</i> Linking Quorum Sensing to Competence for Genetic Transformation. <i>Journal of Bacteriology</i>, 181(16), 5004-5016. | ||
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Latest revision as of 17:51, 14 October 2014
S. pneumoniae σx promoters module
In order to achieve the functionality of pneumosensor, we must have a highly specific reporting system which will only give fluorescent signal under the presence of S. pneumoniae. In search for the suitable gene circuit, the discovery by Prof. Morrison on the competence for genetic transformation in S. pneumoniae which depends on quorum-sensing system to control many competence-specific genes acting in DNA uptake, processing, and integration has provided the ideal framework for this module. (Lee and Morrison, 1999) There is a link between this quorum-sensing system and the competence-specific genes, which is an alternative σx (ComX protein) that serves as a competence-specific global transcription modulator. (Luo and Morrison, 2003) In S. pneumoniae, competence (a state capable of being genetic transformed) happens transiently during the log phase growth, and is regulated by a quorum sensing system utilizing the Competence Signal Peptide (CSP). Upon stimulation by CSP, σx will be expressed and associated with RNA polymerase apoenzyme. The resulting holoenzyme will then be guided by σx to initiate transcription of a set of “late” genes enabling genetic transformation and other unknown functions. Characterized genes regulated by σx were found to contain an 8 base pairs consensus sequence TACGAATA known as the Cin-Box or the Com-Box. (Piotrowski, Luo, & Morrison, 2009). Taking advantage of this competence-specific mechanism, it is now able to produce the S. pneumoniae sensing device of high specificity by incorporating this system into E. coli.
iGEM 2014 Hong_Kong_HKUST Team has cloned σx from S. pneumoniae strain NCTC7465 and characterized its ability to initiate transcription of two downstream promoters with different lengths: PcelA (BBa_K1379000) and PcomFA (BBa_K1379001), which have the consensus Com-Box sequence. Though much information about the promoters is readily available nowadays, its characterization of promoter activity, specificity, sequence, as well as the biomolecular mechanism can be greatly enhanced with further investigations and experiments. Hence, we were interested in reproducing this gene circuit with all the associated genes and promoters to be combined into a single transcriptional unit. Despite the suggested susceptibility to leakage and other factors that may hinder or interrupt the mechanism, researches have reported that the pathway was highly specific to certain environmental conditions and stress, suggesting minimal or no leakage in the entire process. PcelA and PcomFA promoters have high specificity to σx for activation, so genes downstream the promoters will be translated only if σx is present. Hence, by using fluorescence protein as a reporting mechanism, this σx, PcelA and PcomFA promoters system could be further utilized as a specific reporter device in E. coli DH10B strain that could be used by iGEM communities. |
σx and ComW mechanism
To complete the story of competence regulation mechanism from S. Pneumoniae, we would also like to integrate another positive factor involved in competence regulation which was later found out to be ComW. Prof. Morrison's lab released another research paper on the identification of a new component in the regulation of genetic transformation in S. Pneumoniae. The gene comW (SP0018) was found to be regulated by the quorum-sensing system and is required for a high-level of competence (Luo, Li, and Morrison, 2004). Coexpression of ComW with σx restores the accumulation of σx and the expression of late genes as ComW contributes to the stabilization of the alternative sigma factor X against proteolysis by ClpXP and is required for full activity of σx in directing transcription of late competence genes (Piotrowski, Luo, and Morrison, 2009).
Based on these findings, we tried to integrate this ComW into the mechanism to see whether and how the presence of ComW affects σx. We firstly cloned out the comX gene expressing σx, and comW genes from the genomic DNA of S. pneumoniae NCTC 7465 strain. We then used BBa_K880005 (consisting of constitutive promoter BBa_J23100 and strong RBS BBa_B0034) from the BioBricks to express those genes. |
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