Anti-Rat IgM monoclonal antibody, clone NBSN-5 [HRP]

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.

Most genetic disruptions underlying human disease are microlesions, whereas gross lesions are rare with gross deletions being most frequently found (6%). Similar observations have been made in primary immunodeficiency genes, such as BTK, but for unknown reasons the IGHM and DCLRE1C (Artemis) gene defects frequently represent gross deletions (similar to 60%). We characterized the gross deletion breakpoints in IGHM-, BTK-, and Artemis-deficient patients. The IGHM deletion breakpoints did not show involvement of recombination signal sequences or immunoglobulin switch regions. Instead, five IGHM, eight BTK, and five unique Artemis breakpoints were located in or near sequences derived from transposable elements (TE). The breakpoints of four out of five disrupted Artemis alleles were located in highly homologous regions, similar to Ig subclass deficiencies and V-H deletion polymorphisms. Nevertheless, these observations suggest a role for TEs in mediating gross deletions. The identified gross deletion breakpoints were mostly located in TE subclasses that were specifically overrepresented in the involved gene as compared to the average in the human genome. This concerned both long (LINE1) and short (Alu, MIR) interspersed elements, as well as LTR retrotransposons (ERV). Furthermore, a high total TE content (>40%) was associated with an increased frequency of gross deletions. Both findings were further investigated and confirmed in a total set of 20 genes disrupted in human disease. Thus, to our knowledge for the first time, we provide evidence that a high TE content, irrespective of the type of element, results in the increased incidence of gross deletions as gene disruption underlying human disease.