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Nodal marginal zone lymphoma (NMZL) is a primary nodal B-cell lymphoma that shares morphological and immunophenotypic characteristics with extranodal and splenic marginal zone lymphoma. Data on altered genes and signaling pathways are scarce in this rare tumor entity. To gain further insights into the genetic background of NMZL, seven cases were investigated by microarray analysis, G-banding, and FISH. Chromosomal imbalances were observed in 3/7 cases (43%) with gains of chromosome arms 1q, 8q, and 12q being the most frequent findings. Furthermore, we identified a translocation t(11;14)(q23;q32) involving IGH and DDX6. Chromosomal walking, expression analysis, siRNA-mediated gene knockdown and a yeast two hybrid screen were performed for further characterization of the translocation in vitro. In siRNA experiments, DDX6 appeared not to be involved in NF-κB activation as frequently observed for genes promoting lymphomagenesis but was found to interfere with the expression of BCL6 and BCL2 in an NF-κB independent manner. In conclusion, we identified several unbalanced aberrations and a t(11;14) involving IGH and DDX6 providing evidence for a contribution of DDX6 to lymphomagenesis by deregulation of BCL6 in NMZL., (Copyright © 2012 Wiley Periodicals, Inc.)

Purpose: ETV1 has been proposed to be activated by KIT mutations in gastrointestinal stromal tumors (GIST). The aim of the study was to evaluate the clinical role of ETV1 and associated proteins in GIST., Experimental Design: Expressions of ETV1, MAPKAP kinase 2 (MAPKAPK2), phosphorylated p38 MAP kinase (pp38), phosphorylated MSK1 (pMSK1), phosphorylated RSK1, COP1, and KIT protein were determined immunohistochemically in 139 GISTs. Sequence analysis of KIT, PDGFRA, and MAPKAPK2 and FISHs of ETV1 as well as chromosomes 1 and 7 were done., Results: Prominent ETV1 expression was seen in 50% of GISTs, but no correlation with clinical outcome was found. Correlation of ETV1 expression and KIT mutation was seen in 60% of cases. MAPKAPK2 overexpression (n = 62/44.6%) correlated with pp38 expression (P = 0.021, χ(2) test) and alterations of chromosome 1 (n = 17, P = 0.024, χ(2) test). In one of 20 sequenced cases with high MAKAPK2 expression, a putative damaging MAPKAPK2 gene mutation was found. All relapsing GISTs with very low/low risk according to Fletcher showed high MAPKAPK2 and KIT expression. MAPKAPK2 overexpression was an independent prognostic factor for disease-free survival (P = 0.006, Cox regression)., Conclusion: ETV1 is not universally overexpressed in GIST and seems to also be induced by pathways other than KIT mutation. Nevertheless, its clinical relevance is low. Overexpression of ETV1 inhibitor MAPKAPK2 is associated with shorter survival in GIST, indicating a clinically relevant role of this gene not reported previously. Patients with low-risk GISTs showing MAPKAPK2 overexpression might profit from early adjuvant tyrosine kinase inhibitor therapy., (©2012 AACR.)

The gene PRT1 of Arabidopsis, encoding a 45-kD protein with two RING finger domains, is essential for the degradation of F-dihydrofolate reductase, a model substrate of the N-end rule pathway of protein degradation. We have determined the function of PRT1 by expression in yeast (Saccharomyces cerevisiae). PRT1 can act as a ubiquitin protein ligase in the heterologous host. The identified substrates of PRT1 have an aromatic residue at their amino-terminus, indicating that PRT1 mediates degradation of N-end rule substrates with aromatic termini but not of those with aliphatic or basic amino-termini. Expression of model substrates in mutant and wild-type plants confirmed this substrate specificity. A ligase activity exclusively devoted to aromatic amino-termini of the N-end rule pathway is apparently unique to plants. The results presented also imply that other known substrates of the plant N-end rule pathway are ubiquitylated by one or more different ubiquitin protein ligases.

Mutants in the PRT1 gene of Arabidopsis thaliana are impaired in the degradation of a normally short-lived intracellular protein that contains a destabilizing N-terminal residue. Proteins bearing such residues are the substrates of an ubiquitin-dependent proteolytic system called the N-end rule pathway. The chromosomal position of PRT1 was determined, and the PRT1 gene was isolated by map-based cloning. The 45-kDa PRT1 protein contains two RING finger domains and one ZZ domain. No other proteins in databases match these characteristics of PRT1. There is, however, a weak similarity to Rad18p of Saccharomyces cerevisiae. The RING finger domains have been found in a number of other proteins that are involved in ubiquitin conjugation, consistent with the proposed role of PRT1 in the plant N-end rule pathway.