Notes: The authors sought to determine the mechanism by which first-trimester trophoblasts resist FAS ligand-induced apoptosis but remain sensitive to TNFα-mediated apoptosis. First trimester trophoblasts express XAF1 [X-linked inhibitor of apoptosis (XIAP)-associated factor 1], which may be involved in regulating their response to proapoptotic signals. The authors created HaloTag™-XAF1 fusion constructs and transiently transfected the first trimester trophoblast cell line (3A). Cells were labeled with the HaloTag™ TMR ligand, and XAF1 was shown to localize to the cytoplasm. 3A cells transiently transfected with the fusion construct were also separated into cytoplasmic and mitochondrial fractions. The fractions were labeled with HaloTag™ TMR ligand. Expression of the fusion peaked at 48 hours after transfection in both mitochondrial and cytoplasmic fractions. TNFα-treatment of 3A cells induced translocation of endogenous XAF1 to the mitochondria. The authors used the Caspase-Glo® Assays to demonstrate activation of caspase-3 and caspase-9 in response to expression of XAF-1. They also show that caspase-3 activation and XIAP cleavage correlate with translocation of endogenous XAF1 to mitochondria. Viability of 3A and primary trophoblasts over expressing XAF1 was evaluated using the CellTiter® 96 AQueous One-Solution Assay. (3760)

Notes: This paper describes work to use the HaloTag™ Interchangeable Protein Labeling Technology for the specific conjugation of proteins to quantum dots. The authors used the pHT2 vector to create a Renilla luciferase (Luc 8)/HaloTag™ Protein fusion that contained a 6X polyhistidine tag. The fusion protein was purified over a nickel affinity resin. They synthesized a HaloTag™ ligand for conjugation to the quantum dots. The ligand was designed to orient the ligand away from the quantum dot surface to minimize steric hindrance between the HaloTag™ fusion protein and the quantum dots upon interaction of the fusion protein with the ligand. The authors used BRET emission to evaluate conjugation of the HaloTag™ fusion protein to the quantum dots. They conclude that using this technology, they were able to conjugate a bioluminescent protein to quantum dots, creating self-illuminating quantum dots. Furthermore, they suggest that the mild conjugation conditions used may allow in vivo labeling of proteins or cells using quantum dots. (3490)

Notes: This paper highlights the first use of the HaloTag™ Interchangeable Protein Labeling Technology in plant cells. The cDNA for the HaloTag™ protein was amplified by PCR from the pHT2 Vector and cloned into the pGEM^®-T Easy^® Vector, from which it was excised and transferred to a second vector where its expression was under the control of the cauliflower mosaic virus (CaMV)-³⁵S promoter. The construct was transformed into tobacco protoplasts and bioballistically transformed into tobacco leaf cells. Localization was followed using the HaloTag™ TMR and diAcFAM Ligands. (3503)

Notes: HaloTag™ Interchangeable Labeling Technology was used to specifically label engineered dynein produced in Saccharomyces cerevisiae. The HaloTag™ Protein was added in-frame with either the 5´ or 3´ end of the coding sequence of various engineered dynein molecules. The authors report being able to label the dynein in specific locations using fluorescent dyes or quantum dots. HaloTag™ TMR Ligand was used to covalently label dynein to directly visualize dynein motor movement using total internal reflection fluorescence microscopy. HaloTag™ Biotin Ligand was used to label dynein with streptavidin quantum dots. (3504)