Difference between revisions of "Part:BBa K2549040"

Revision as of 12:55, 17 October 2018

KRAB-dNLS-ZF21.16

This part is one of the downstream elements of our amplifier. It is constructed by fusing KRAB (Part:BBa_K2549055), dNLS (Part:BBa_K2549056) and ZF21.16 (Part:BBa_K2549046), from N terminal to C terminal. KRAB is a strong transcription repressor. dNLS, which is short for destroyable nuclear localization sequence, is able to guide the fusion protein to be located to the nucleus without TEV protease. It is cleaved and unable to guide the fusion protein when TEV protease exist. Thus when coexpressed with NLS-TEVp (Part:BBa_K2549041), it is cleaved and the transcription repression function cannot be conducted.

Biology

TEV protease-based transcription regulation or proteolysis-only activity

TEV protease is widely used in synthetic biology for its high cleavage specificity (targetting amino acids sequence ENLYFQG/S between QG or QS)^[1] and cleaves and high efficiency (optimized by RB Kapust et al to remove autolysis)^[2]. Rossner MJ et al have demonstrated the TEV activity-dependent activation of several reporters^[3]. In our system, we set the TEV protease specific cleavage site into the spacer region of the nuclear localization sequence^[4], which is the core design of the TEV protease-based complex logic gates.

Rossner MJ et al stated:TEV protease activity can be monitored with either inactivated transcription factors (‘transcription-coupled’ reporters) or inactivated reporter proteins (‘proteolysis-only’ reporters). We designed a ‘transcription-coupled’ TEV reporter at the membrane (TM-GV) by fusing a transcription factor composed of a yeast Gal4 DNA-binding domain and the herpes simplex VP16 transactivation domain (GV) to an hemagglutinin (HA)-tagged transmembrane region from the human PDGF-a receptor via a TEV-protease cleavage site ENLYFQ'G . After TEV protease cleavage, GV can translocate into the nucleus and induce reporter gene expression via five clustered Gal4-responsive cis elements. We constructed membrane localized ‘proteolysis-only’ reporters containing a luciferase moiety. We flanked GV N- and C-terminally by tevS sites and ERT2 domains (GV-2ER) thereby trapping the GV transcription factor reporter unit in the cytoplasm.

For more details about TEV protease, please refer to our TEVp (Part:BBa_K2549013).

Characterization

It works as we designed.

TEVp-based IMPLY gate. A degradable EGFP (d2EGFP) is linked downstream the promoter to indicate the expression level of it. DBD, DNA binding domain which is zinc finger in our assay. AD or SD, activating- or silencing-form transcriptional domain. RE, responsive elements. RFI, relative fluorescence intensity.

Flow cytometry results indicate that when KRAB-dNLS-ZF21.16 exists while TEVp doesn't exist that the expression level of d2EGFP is repressed. When TEVp and KRAB-dNLS-ZF21.16 coexist, TEVp cleaves dNLS and prevents KRAB from entering into the nucleus. Thus the repression is not severe as when KRAB-dNLS-ZF21.16 is present while TEVp is absent. Sequence and Features

References

1. ↑ Release of proteins and peptides from fusion proteins using a recombinant plant virus proteinase. Parks TD, Leuther KK, Howard ED, Johnston SA, Dougherty WG. Anal Biochem, 1994 Feb;216(2):413-7 PMID: 8179197; DOI: 10.1006/abio.1994.1060
2. ↑ Tobacco etch virus protease: mechanism of autolysis and rational design of stable mutants with wild-type catalytic proficiency. Kapust RB, Tözsér J, Fox JD, ..., Copeland TD, Waugh DS. Protein Eng, 2001 Dec;14(12):993-1000 PMID: 11809930
3. ↑ Monitoring regulated protein-protein interactions using split TEV. Wehr MC, Laage R, Bolz U, ..., Nave KA, Rossner MJ. Nat Methods, 2006 Dec;3(12):985-93 PMID: 17072307; DOI: 10.1038/nmeth967
4. ↑ Two interdependent basic domains in nucleoplasmin nuclear targeting sequence: identification of a class of bipartite nuclear targeting sequence. Robbins J, Dilworth SM, Laskey RA, Dingwall C. Cell, 1991 Feb;64(3):615-23 PMID: 1991323