Team:Penn/AssayValidation
From 2013.igem.org
Assay Validation
We have designed standardized bisulfite sequencing primers.
Bisulfite sequencing is a good next step after restriction digest to further characterize functional site-specific methylases, but it is inherently very difficult to design good primers. People use advanced algorithms for primer design that are still not guaranteed to successfully sequence some sequences. We went through 8 sets of primers, most of which did not show the proper bias to amplify only bisulfite converted DNA. Primer Set 2 was successful and is included with our MaGellin plasmid, much like VF and VR are included as standardized biobrick sequencing primers (Figure 1).MaGellin effectively detects methylation in vitro.
First, we tested MaGellin with a purified methylase in vitro. The results made it clear that MaGellin can detect methylation at both the “target” and “off-target” site (Figure 2). MaGellin is also sensitive to various degrees of methylation (Figure 3). These experiments helped us optimize the ideal amount of plasmid and restriction enzyme to use in any study moving forward.MaGellin detects methylation in vivo.
We expressed M.SssI in vivo and compared it with purified M.SssI used on the plasmid in vitro. In both cases, we saw similar full methylation of the plasmid, confirming that MaGellin can express methylases and report their activity in vivo (Figure 4).Summary
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We have created MaGellin, a new technology that facilitates screening novel DNA binding domain – methylase fusion proteins
- Our assay is less expensive and faster than existing methods
- We have eliminated noise associated with previous studies
- We have a system with clear input/output
- Our assay lends itself to high throughput screening of many different proteins
- We are releasing it alongside an open source data analysis software package which streamlines the entire screening process