Notes: These authors set out to determine how TET2 and TET3 proteins are involved in epigenetic regulation. To characterize proteins that interact with TET, the authors expressed full-length TET1, TET2 and TET3 as HaloTag® fusion proteins and performed protein pull-downs. They identified novel interactions between all three TET proteins and O-GlcNAc transferase (OGT), which catalyzes the addition of N-acetylglucosamine (GlcNAc) to numerous transcription factors, regulatory proteins and histones to activate or inhibit the target protein or recruit additional proteins. In this paper, they focused on TET2 and TET3, which showed the strongest interaction with OGT. They mapped TET2, TET3 and OGT binding throughout  the genome by expressing these proteins as HaloTag® fusion proteins in HEK293T cells, crosslinking the proteins and DNA, then capturing the fusion proteins and associated DNA fragments and performing high-throughput sequencing to show that TET2/3 and OGT colocalize at active gene promoters and were tightly clustered near transcription start sites.

For expression of HaloTag® fusion proteins and controls, HEK-293 cells were plated at 12 ×10⁶ cells in a 150mm dish and grown to 70–80% confluency before transfection with 30µg of plasmid using the FuGENE® HD Transfection Reagent.

To assess whether TET2/3-OGT activity affects the interaction of SET1/COMPASS with chromatin, the authors used bioluminescence resonance energy transfer (BRET). They created a fusion protein consisting of the H3K4 methyltransferase SETD1A and NanoLuc® luciferase as the energy donor and a fluorescently labeled histone H3.3-HaloTag® fusion protein as the energy acceptor.  These BRET experiments confirmed that TET2/3-OGT activity is necessary for SET1/COMPASS complex function and showed that TET and OGT activities promote binding of SETD1A, a component of the SET1/COMPASS complex, to chromatin. This binding increases H3K4me3 levels. Thus, the authors’ data support a TET2/3-OGT-mediated mechanism for regulating the SET1/COMPASS complex and thus H3K4me3. (4262)

Notes: In this study, the L. pneumophila protein Lem3 was expressed as a HaloTag^® fusion protein and purified using HaloLink™ Resin. Lem3 was first cloned into the pFN22K HaloTag^® Vector and the resultant HaloTag-Lem3 protein was expressed in Single-Step (KRX) competent cells before purification using the HaloTag^® Protein Purification System. Lem3 was cleaved from the HaloLink™ Resin using TEV protease.

  (4350)

Notes: This paper provides an overview of the many applications of HaloTag® Technology. The authors describe the development of the technology, focusing on it's multifunctional utility for protein imaging, protein isolation and display, and in the study of protein complexes and interactions. They also discuss it's potential to facilitate proteomics research studies across complex biological systems at the biochemical, cell-based and whole animal level. (4325)