Difference between revisions of "Part:BBa K404108"

Latest revision as of 19:59, 16 October 2019

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.

Figure 10: Flow cytometry analysis of vectorplasmid without (left) and with (right) hGH. For viral particle production, AAV-293 cells were transfected with the reassembled vector plasmid (BBa_K404119) or the reference plasmid, respectively. A: Gating non transduced cells (control); subcellular debris and cellular aggreates can be distinguished from single cells by size, estimated forward scatter (FS Lin) and granularity, estimated side scatter (SS Lin) B: Non-transduced cells plotted against cells expressing mVenus (Analytical gate was set such that 1% or fewer of negative control cells fell within the positive region (R5) C: Gating transduced cells (R2 ≙ R14) (plasmids used for transfection: pGOI: pSB1C3_lITR_CMV_beta-globin_mVenus_hGH_rITR (pSB1C3_mVenus: BBa_K404119), pHelper, pRC. D: Transduced cells plotted against cells expressing mVenus. R10 comprises transduced cells detected by mVenus fluorescence. E: Overlay of non-transduced (red) and transduced (green).

F: Gating non-transduced cells (control). G: Non-transduced cells plotted against cells expressing mVenus (R5). H: Gating transduced cells (R14 ≙ R2) (plasmids used for transfection: pGOI: pAAV_mVenus, pHelper). I: Transduced cells plotted against cells expressing mVenus. R10 comprises transduced cells detected by mVenus fluorescence. J: Overlay of non-transduced (red) and transduced (green) cells plotted against mVenus expression.

Flow cytometry analysis of vectorplasmids with and without hGH terminator. YFP expression of viral genomes was determined by flow cytomery after 24-hour post infection. Results demonstrate that mVenus expression of vectorplasmids lacking the hGH terminator is reduced significantly proving that the polyadenylation signal is essential for viral gene expression using recombinant viral vectors engineered by using components of the Virus Construction Kit.

Secondary Structure

File:Mfold-K404108-1.png

References

Danckwardt, S., Hentze, M. W., & Kulozik, A. E. (2008). 3' end mRNA processing: molecular mechanisms and implications for health and disease. The EMBO journal, 27(3), 482-98. doi: 10.1038/sj.emboj.7601932.
Millevoi, S., Loulergue, C., Dettwiler, S., Karaa, S. Z., Keller, W., Antoniou, M., et al. (2006). An interaction between U2AF 65 and CF I(m) links the splicing and 3' end processing machineries. The EMBO journal, 25(20), 4854-64. doi: 10.1038/sj.emboj.7601331.

Measurement

• [http://openwetware.org/wiki/Cconboy:Terminator_Characterization/Results How these parts were measured]