Part:BBa_K404108
Usage and Biology
| beta-globin intron | |
|---|---|
| |
| BioBrick Nr. | BBa_K404108 |
| RFC standard | RFC 10 |
| Requirement | pSB1C3 |
| Source | pAAV_MCS |
| Submitted by | [http://2010.igem.org/Team:Freiburg_Bioware FreiGEM 2010] |
The iGEM team Freiburg provides an hGH plolyadenylation sequence within the ‘Virus Construction Kit’ due to the fact that almost every eukaryotic mRNA is processed at their 3´ and 5´end except for histone mRNAs (Millevoi et al., 2006). Pre-mRNAs contain two canonical conserved sequences. First, the polyadenylation signal “AATAAA” which is recognized by the multiprotein complex and second the GT-rich region (downstream sequence element, DSE) which is located 30 nucleotides downstream of the cleavage site. The assembled 3´end-processing machinery cleaves the mRNA transcript immediately after a CA-nucleotide therefore defining the cleavage site (Danckwardt, Hentze, & Kulozik, 2008).
Characterization
Recombinant AAV genomes were engineered containing the inverted terminal repeats (ITRs), a strong eukaryotic promoter and mVenus as gene of interest with and without the hGH terminator signal. Transduction of HT1080 cells with viral particles containing the rAAV genomes and measuring mVenus expression 24-hours post infection by flow cytometry demonstrated that transgene expression of the constructs lacking the hGH termination signal is significantly reduced. The iGEM team Freiburg_Bioware 2010 therefore suggests using the provided hGH termination signal within the Virus Construction Kit for optimal gene expression.
Since cloning does not confirm biological activity, we analyzed the plasmids and their functional components, hGH terminator and beta-globin intron, in cell culture. Assembled plasmids have been cotransfected, using AAV-293 cells, which provide the stable integrated E1A and E1B genes, with helper plasmids required for capsid assembly and genome encapsidation (pRC and pHelper) in a molar ratio of 1:1:1 (pGOI:pRC:pHelper). Virus particles containing the single stranded DNA were harvested 72-hours post transfection and HT1080 cells transduced with constant volumes of viral vectors. 48-hours post infection; transduced cells expressing the gene of interest were analyzed by flow cytometry.
Recombinant vectorplasmids were engineered containing the inverted terminal repeats (ITRs), a strong eukaryotic promoter (CMV promoter: BBa_K404102) and mVenus as gene of interest with and without the hGH terminator signal. Transduction of HT1080 cells with constant volume of viral particles containing the vectorplasmids and measuring mVenus expression 24-hours post infection by flow cytometry demonstrated that transgene expression of the constructs lacking the hGH termination signal is significantly reduced as shown in confirming the expected results that hGH is essential for mRNA processing. The iGEM team Freiburg_Bioware 2010 therefore suggests using the provided hGH termination signal within the Virus Construction Kit for optimal gene expression.
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