Inactivating mutations and overexpression of BCL10, a caspase recruitment domain-containing gene, in MALT lymphoma with t(1;14)(p22;q32).

Mucosa-associated lymphoid tissue (MALT) lymphomas most frequently involve the gastrointestinal tract and are the most common subset of extranodal non-Hodgkin lymphoma (NHL). Here we describe overexpression of BCL10, a novel apoptotic signalling gene that encodes an amino-terminal caspase recruitment domain (CARD), in MALT lymphomas due to the recurrent t(1;14)(p22;q32). BCL10 cDNAs from t(1;14)-positive MALT tumours contained a variety of mutations, most resulting in truncations either in or carboxy terminal to the CARD. Wild-type BCL10 activated NF-kappaB but induced apoptosis of MCF7 and 293 cells. CARD-truncation mutants were unable to induce cell death or activate NF-kappaB, whereas mutants with C-terminal truncations retained NF-kappaB activation but did not induce apoptosis. Mutant BCL10 overexpression might have a twofold lymphomagenic effect: loss of BCL10 pro-apoptosis may confer a survival advantage to MALT B-cells, and constitutive NF-kappaB activation may provide both anti-apoptotic and proliferative signals mediated via its transcriptional targets.

Cloning and chromosomal localization of the gene encoding human cyclin D-binding Myb-like protein (hDMP1).

The murine transcription factor murine cyclin D-binding Myb-like protein (mDmp1) arrests the cell cycle in G1 phase, through an activity that can be overridden by direct interaction with the D-type cyclins. Here, we describe the identification, sequence, chromosomal localization, and expression of the human cognate, hDMP1. The hDMP1 cDNA contains a 2280bp open reading frame that shares a high degree of identity with the mDmp1 coding region. The 4.4kb hDMP1 messenger RNA is ubiquitously expressed in normal human tissues, with highest levels in testis and substructures within the brain. By use of fluorescence in situ hybridization with a human genomic P1 probe, we assigned hDMP1 to chromosome 7, band q21. This chromosomal region is frequently deleted as part of the 7q-minus and monosomy 7 abnormalities of human acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We analyzed hDMP1 copy number by fluorescence in situ hybridization in leukemic blasts from nine patients with abnormalities of the long arm of chromosome 7, and in each case one allele of the hDMP1 gene was deleted. Functional analysis of the mDmp1 protein has shown that it negatively regulates cell proliferation, which suggests that this gene is a candidate suppressor of malignant transformation. Further study will be needed to determine whether gene-specific mutations implicate hDMP1 as a tumor suppressor in acute leukemias with deletions of the long arm of chromosome 7 or in other types of human malignancy.

Sequence of the Sendai virus L gene: open reading frames upstream of the main coding region suggest that the gene may be polycistronic.

The sequence of the L gene of Sendai virus, encompassing 6799 nucleotides, has been determined, completing the primary sequence of the entire virus genome. An open reading frame beginning at position 569 codes for a basic protein of 2048 amino acids with an estimated Mr of 231,608. No nucleotide sequence similarities with the analogous L gene of vesicular stomatitis virus were observed. However, comparison of the deduced amino acid sequences of both proteins revealed a conserved 18 amino acid sequence that may have functional significance. Two additional overlapping reading frames which precede the L protein sequence could encode proteins with MrS of 6474 and 14,026, suggesting that the gene is polycistronic.

Two candidate downstream target genes for E2A-HLF.

The E2A-HLF fusion gene, formed by the t(17;19)(q22;p13) chromosomal translocation, is thought to drive the leukemic transformation of early B-cell precursors by repressing an evolutionarily conserved apoptotic pathway. To test this hypothesis, we sought to identify downstream targets of E2A-HLF in t(17;19)+ pro-B leukemia cells (UOC-B1) that had been transfected with a zinc-inducible vector encoding a dominant-negative suppressor (E2A-HLF[dn]) of the oncoprotein. Representational difference analysis of mRNAs from E2A-HLF(dn)+ UOC-B1 cells grown with (E2A-HLF inactive) or without (E2A-HLF active) the addition of zinc yielded several differentially expressed cDNA fragments that were individually subcloned. Two of the clones, designated F-5 and G-4, hybridized with mRNAs that were upregulated by E2A-HLF. Levels of both transcripts declined sharply within 8 to 12 hours after suppression of E2A-HLF DNA-binding activity, becoming undetectable after 96 hours. The F-5 cDNA was identified as a portion of ANNEXIN VIII, whose product was expressed in promyelocytic leukemia cells and UOC-B1 cells, but not in other leukemic cell lines. A novel full-length cDNA cloned with the G-4 fragment encoded a protein that we have named SRPUL (sushi-repeat protein upregulated in leukemia). It is normally expressed in heart, ovary, and placenta, but could not be detected in leukemic cell lines other than UOC-B1. Neither protein prevented apoptosis in interleukin-3-dependent murine pro-B cells, suggesting that they have paraneoplastic roles in leukemias that express E2A-HLF, perhaps in the disseminated intravascular coagulopathy and hypercalcemia that characterize these cases.