Citations

The product of the Nijmegen breakage syndrome gene (NBS1) plays crucial roles in DNA damage response through its association with many proteins, including MRE11 and RAD50. However, it remains to be determined exactly how NBS1 accumulates at or near DNA double-strand breaks. Here we report that MDC1 directly binds to NBS1 and targets NBS1 to the sites of DNA damage. The MDC1–NBS1 interaction occurs through a specific region (residues 200–420) of MDC1, which contains multiple consensus casein kinase 2 (CK2) phosphorylation sites. In addition, this interaction requires both the forkhead-associated (FHA) and tandem BRCA1 C-terminal (BRCT) domains of NBS1. Disruption of the MDC1–NBS1 interaction results in failure of NBS1 accumulation at DNA double-strand breaks and impairment of intra-S checkpoint activation. These studies provide important mechanistic insights as to how MDC1 regulates NBS1 and the intra-S-phase checkpoint in response to DNA damage.

Background and Purpose— In stroke and other brain disorders, severely affected phenotypes often impair decision-making capacity. Severity is in part under genomic control. Therefore, scientifically valid research into genetic risk may require inclusion of such impaired individuals. U.S. Federal regulations do not detail rules governing enrollment of adults with impaired decision-making capacity into genetic research. Rather, policy and practice are locally determined. This study was conducted to obtain data on how investigators and IRBs handle surrogate authorization to enroll probands into a genetic study where some may lack capacity because of ischemic stroke. Methods— Sequential surveys of sites from an ongoing North American study investigating genetic risks for ischemic stroke (2003: 49 sites, response rate=100%; 2007: 53 sites; response rate=91%) assessed whether and how investigators enroll adults with impaired decision-making capacity and determined frequency of IRB approval for enrollment by surrogate authorization. Results— Approximately 40% of sites report that their IRBs do not approve surrogate authorization to enroll stroke patients—43% (21/49) in 2003 and 35% (17/48) in 2007. Thirty-three percent of sites report evaluating eligible adults who lacked capacity to provide their own informed consent; 18% (9/49) in 2003 and 15% (7/48) in 2007 have enrolled these individuals. Surrogate enrollment is the most common method used. Most sites have not enrolled any individual lacking capacity to give his or her own consent. Conclusions— Our study suggests that enrollment by surrogate authorization into stroke genetic research is often not approved by IRBs, and even when allowed is frequently not used. For disorders like stroke, this situation has significant implications for scientific validity.

Purpose The combination of oral weekly cyclophosphamide and alternate day prednisone is a convenient regimen for relapsed/refractory multiple myeloma (MM), and we sought to improve its efficacy by adding bortezomib, a proteasome inhibitor with proven antimyeloma activity. Patients and Methods We conducted a phase I-II trial evaluating six dose levels to define the maximum tolerated dose (MTD) of this combination in relapsed/refractory MM. An additional 10 patients were evaluated at the highest dose level reached. Results Thirty-seven patients were treated on this study. The MTD was not defined. Both of the highest dose levels of bortezomib tested (1.3 mg/m 2 on days 1, 4, 8, and 11 and 1.5 mg/m 2 on days 1, 8, and 15, each on a 28-day cycle) could be safely given with cyclophosphamide 300 mg/m 2 per week and prednisone. At these dose levels, the overall response rate was 95% (complete responses [CR] plus partial response plus minimal response), with CR observed in more than 50% of patients. The weekly bortezomib regimen resulted in fewer instances of grade 3 thrombocytopenia and grade 1 to 2 peripheral neuropathy; the 1-year progression-free and overall survival probabilities with this dose level were 83% (95% CI, 73% to 96%) and 100%, respectively. Conclusion Weekly bortezomib 1.5 mg/m 2 plus oral cyclophosphamide and prednisone produces an unprecedented response rate and encouraging 1-year survival in relapsed/refractory patients with MM. Further evaluation of this promising regimen is warranted both in relapsed and newly diagnosed disease.

Eps15 (EGFR pathway substrate clone 15) is well known for its role in clathrin-coated vesicle formation at the plasma membrane through interactions with other clathrin adaptor proteins such as AP-2. Interestingly, we observed that in addition to its plasma membrane localization, Eps15 is also present at the trans-Golgi network (TGN). Therefore, we predicted that Eps15 might associate with clathrin adaptor proteins at the TGN and thereby mediate the formation of Golgi-derived vesicles. Indeed, we have found that Eps15 and the TGN clathrin adaptor AP-1 coimmunoprecipitate from rat liver Golgi fractions. Furthermore, we have identified a 14-amino acid motif near the AP-2–binding domain of Eps15 that is required for binding to AP-1, but not AP-2. Disruption of the Eps15–AP-1 interaction via siRNA knockdown of AP-1 or expression of mutant Eps15 protein, which lacks a 14-amino acid motif representing the AP-1 binding site of Eps15, significantly reduced the exit of secretory proteins from the TGN. Together, these findings indicate that Eps15 plays an important role in clathrin-coated vesicle formation not only at the plasma membrane but also at the TGN during the secretory process.