chromatin immunoprecipitation (ChIP)

17 Papers Using GFP-Trap, 12 Since 2009

1. MacKay C, Déclais AC, Lundin C et al. (2010). Identification of KIAA1018/FAN1, a DNA repair nuclease recruited to DNA damage by monoubiquitinated FANCD2. Cell 142:65-76.

2. Babiano R, de la Cruz J. (2010). Ribosomal protein L35 is required for 27SB pre-rRNA processing in Saccharomyces cerevisiae. Nucleic Acids Res 2010 Apr 14.

3. Fulcher AJ, Dias MM, Jans DA. (2010). Binding of p110 retinoblastoma protein inhibits nuclear import of simian virus SV40 large tumor antigen. J Biol Chem. 285:17744-53.

4. Taniue K, Nishida A, Hamada F et al. (2010). Sunspot, a link between Wingless signaling and endoreplication in Drosophila. Development. 137:1755-64.

5. Rottach A, Frauer C, Pichler G et al. (2010). The multi-domain protein Np95 connects DNA methylation and histone modification. Nucleic Acids Res. 38:1796-804.

6. Boulon S, Ahmad Y, Trinkle-Mulcahy L et al. (2010). Establishment of a protein frequency library and its application in the reliable identification of specific protein interaction partners. Mol Cell Proteomics. 9:861-79.

7. Schornack S, Fuchs R, Huitema E et al. (2009). Protein mislocalization in plant cells using a GFP-binding chromobody. Plant J. 60:744-54.

8. Fellinger K, Bultmann S, Rothbauer U et al. (2009). Np95 interacts with de novo DNA methyltransferases, Dnmt3a and Dnmt3b, and mediates epigenetic silencing of the viral CMV promoter in embryonic stem cells. EMBO Rep. 10:1259-64.

9. Muñoz IM, Hain K, Déclais AC et al. (2009). Coordination of structure-specific nucleases by human SLX4/BTBD12 is required for DNA repair. Mol Cell. 35:116-27.

10. Webby CJ, Wolf A, et al. (2009). Jmjd6 Catalyses Lysyl-Hydroxylation of U2AF65, a Protein Associated with RNA Splicing. Science. 325:90-93.

11. Rogowski K et al. (2009). Evolutionary divergence of enzymatic mechanisms for posttranslational polyglycylation. Cell. 137: 1076-87.

12. Frauer C, Leonhardt H, (2009) A versatile non-radioactive assay for DNA methyltransferase activity and DNA binding. Nucleic Acid Res. 35: 5402-5409.

13. Trinkle-Mulcahy L et al., (2008) Identifying specific protein interaction partners using quantitative mass spectrometry and bead proteomes. J Cell Biol. 183: s223-39.

14. Rothbauer U, Leonhardt H, (2008) Connecting Biochemistry and Cell Biology with Nanobodies. Zellbiologie aktuell 34: 9-12.

15. Rothbauer U et al., (2008) A versatile nanotrap for biochemical and functional studies with fluorescent fusion proteins. Mol Cell Proteomics 7: 282-289.

16. Agarwal N et al., (2007) MeCP2 interacts with HP1 and modulates its heterochromatin association during myogenic differentiation. Nucleic Acid Res.35: 5402-5409.

17. Rothbauer U et al., (2006) Targeting and tracing antigens in live cells with fluorescent nanobodies. Nat Methods 3: 887-889.

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Immunoprecipitation Tags

Immunoprecipitation is a process of isolating a protein as an antigen by using antibodies against it. It is a powerful tool for studying proteins in biological samples and, in case of Co-IP (meaning immunoprecipitation of complexes containing a known antigen), for analyzing protein-protein interactions. Similar technologies such as chromatin immunoprecipitation (ChIP), RNA immunoprecipitation (RIP), or crosslinked and iImmunoprecipitation of RNA-protein complexes (CLIP) aid analysis of protein-DNA or protein-RNA interactions.

The major obstacle for achieving effective immunoprecipitation is the difficulty of finding usable antibodies against a target of interest. A common practice is to use tags that are fused to the C- or N-terminus of the target protein, thereby any validated, commercially available antibody can be used for co-IP in different experimental systems. However, caution must be exercised against potential interference of biological functions from the added tags. In general, one should choose tags that have been tested in many situations and proven non-interfering; still, each biological system is different. Independent validation or supporting data should be used when interpreting results from tag-based co-IP.

Tags are often selected based on high quality and commercially available antibodies. Most commonly used tags include: FLAG, Myc, HA, V5, T7, and His, which are quite small in size and in theory less likely to interfere. GST and GFP are in between 20-30kDa, but they are well documented to form self-contained and stable structures independent of their fusion partners and proved to not interfere in many cases. GST can bind to glutathione beads directly, therefore a top choice for pulldown experiments. GFP or other FPs as tags have the advantages of being also a visualization module to follow the protein both inside cells and during pulldown. However, previously available anti-GFP antibodies, either polyclonal or monoclonal, are not comparable to those against other tags, thereby limiting the use of GFP as fusion tag in pulldown experiments.

GFP-Trap, a recent addition to anti-tag antibodies, is an E. coli expressed, single domain fragment derived from camelid heavy chain antibodies (VHH antibodies) with much higher stability, specificity, and affinity, making GFP based pulldown quantitative. This recent advancement should make GFP in line to become the most suitable tags for many aforementioned precipitation experiments.

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