Mouse Anti-Mouse Igh6-4 Hybridoma [NC97]

A transcriptional enhancer, E mu, was defined in the IGH locus of the Pekin duck, Anas platyrhynchos. Regions of DNA from the JH to IGHM intron were cloned into reporter constructs containing the SV40 promoter and transiently transfected into chicken B and T lymphocytes. A strong transcriptional activity, of several hundred-fold greater than that of a reporter construct with the promoter alone, was localized to a 281 bp region that contains 2 E-box motifs, CAGCTG. This fragment showed enhancer activity in both orientations and was active in chicken B cells but not in T cells. When the activity of the enhancer was tested in constructs without a promoter, it showed high transcriptional activity in the forward orientation, but much less activity (by two orders of magnitude) when tested in the reverse orientation. This suggests that the fragment contains not only enhancer activity but may contain promoter activity analogous to that of the I mu promoter described in mammals. Thus it appears that the location, but not the fine structure, of the E mu enhancer was established before the evolutionary divergence of the avian and mammalian lineages some 300 Myr ago. (c) 2006 Elsevier Ltd. All rights reserved.

Clathrin is a protein expressed ubiquitously that has important functions in membrane trafficking and mitosis. Two different gene fusions involving clathrin heavy chain (CHC) have been described in human cancers. These involve either anaplastic lymphoma kinase (ALK) or transcription factor binding to IGHM enhancer 3 (TFE3) and raise the possibility that altered clathrin function in cells expressing the fusion proteins could contribute to oncogenesis. In the present study, we tested the functions of CHC-ALK and CHC-TFE3 in endocytosis and mitosis. CHC-ALK is comparable to full-length CHC in both functions indicating that malignant transformation in cells expressing CHC-ALK is not because of any change in clathrin function. CHC-TFE3 is not functional in endocytosis, but can substitute for CHC in mitosis. CHC-TFE3 causes prolonged interphase that is attributed to the TFE3 portion of the protein. We also describe how CHC-TFE3 is a dimer. This suggests that clathrin's proposed role in intermicrotubule bridging can be fulfilled not only by trimers but also by dimers. Finally, this study shows that the membrane trafficking and mitotic functions of clathrin are independent and separable.