ZNF384

Abstract: The oncogenic mechanisms underlying acute lymphoblastic leukemia (ALL) in adolescents and young adults (AYA; 15-39 years old) remain largely elusive. Here we have searched for new oncogenes in AYA-ALL by performing RNA-seq analysis of Philadelphia chromosome (Ph)-negative AYA-ALL specimens (n = 73) with the use of a next-generation sequencer. Interestingly, insertion of D4Z4 repeats containing the DUX4 gene into the IGH locus was frequently identified in B cell AYA-ALL, leading to a high level of expression of DUX4 protein with an aberrant C terminus. A transplantation assay in mice demonstrated that expression of DUX4-IGH in pro-B cells was capable of generating B cell leukemia in vivo. DUX4 fusions were preferentially detected in the AYA generation. Our data thus show that DUX4 can become an oncogenic driver as a result of somatic chromosomal rearrangements and that AYA-ALL may be a clinical entity distinct from ALL at other ages.

Abstract: Fusion genes involving ZNF384 have recently been identified in B-cell precursor acute lymphoblastic leukemia, and 7 fusion partners have been reported. We further characterized this type of fusion gene by whole transcriptome sequencing and/or polymerase chain reaction. In addition to previously reported genes, we identified BMP2K as a novel fusion partner for ZNF384. Including the EP300-ZNF384 that we reported recently, the total frequency of ZNF384-related fusion genes was 4.1% in 291 B-cell precursor acute lymphoblastic leukemia patients enrolled in a single clinical trial, and TCF3-ZNF384 was the most recurrent, with a frequency of 2.4%. The characteristic immunophenotype of weak CD10 and aberrant CD13 and/or CD33 expression was revealed to be a common feature of the leukemic cells harboring ZNF384-related fusion genes. The signature gene expression profile in TCF3-ZNF384-positive patients was enriched in hematopoietic stem cell features and related to that of EP300-ZNF384-positive patients, but was significantly distinct from that of TCF3-PBX1-positive and ZNF384-fusion-negative patients. However, clinical features of TCF3-ZNF384-positive patients are markedly different from those of EP300-ZNF384-positive patients, exhibiting higher cell counts and a younger age at presentation. TCF3-ZNF384-positive patients revealed a significantly poorer steroid response and a higher frequency of relapse, and the additional activating mutations in RAS signaling pathway genes were detected by whole exome analysis in some of the cases. Our observations indicate that ZNF384-related fusion genes consist of a distinct subgroup of B-cell precursor acute lymphoblastic leukemia with a characteristic immunophenotype, while the clinical features depend on the functional properties of individual fusion partners.

Abstract: p130(cas) (Cas) is a docking protein that contains an SH3 domain and multiple tyrosine residues. p130(cas) is located at focal adhesions, is tyrosine phosphorylated in response to integrin stimulation, and is thought to transmit signals, via c-Crk and other proteins, for the remodeling of actin stress fibers and cell movement. In a search for the ligands of the SH3 domain of p130(cas) by far-Western screening, we cloned a novel protein named CIZ (for Cas-interacting zinc finger protein). CIZ consists of the following: a putative leucine zipper; a serine/threonine-rich region; a proline-rich sequence; five, six, or eight Kruppel-type C(2)H(2) zinc fingers; and the glutamine-alanine repeat. CIZ binds Cas in cells and is located in the nucleus and at focal adhesions. We showed that CIZ is a nucleocytoplasmic shuttling protein, by using the transient interspecies heterokaryon formation assay. In order to search for the targets of CIZ in nucleus, we determined the DNA binding consensus of CIZ as (G/C)AAAAA(A) by cyclic amplification and selection of targets analysis. The consensus-like sequences are found in several promoters of matrix metalloproteinases (MMPs), which are the enzymes used to degrade the extracellular matrix proteins. CIZ binds to a consensus-like sequence in the MMP-1 (collagenase) promoter. Overexpression of CIZ upregulates the transcriptions from MMP-1, MMP-3 (stromelysin), and MMP-7 (matrilysin) promoters, and this transactivation was enhanced in the presence of Cas. Furthermore, the stable overexpression of CIZ promoted the production of MMP-7 in culture medium. In summary, CIZ, a novel zinc finger protein, binds Cas, is a nucleocytoplasmic shuttling protein, and regulates the expression of MMPs.

Abstract: Chromosomal translocations are a genomic hallmark of many hematologic malignancies. Often as initiating events, these structural abnormalities result in fusion proteins involving transcription factors important for hematopoietic differentiation and/or signaling molecules regulating cell proliferation and cell cycle. In contrast, epigenetic regulator genes are more frequently targeted by somatic sequence mutations, possibly as secondary events to further potentiate leukemogenesis. Through comprehensive whole-transcriptome sequencing of 231 children with acute lymphoblastic leukemia (ALL), we identified 58 putative functional and predominant fusion genes in 54.1% of patients (n = 125), 31 of which have not been reported previously. In particular, we described a distinct ALL subtype with a characteristic gene expression signature predominantly driven by chromosomal rearrangements of the ZNF384 gene with histone acetyltransferases EP300 and CREBBP ZNF384-rearranged ALL showed significant up-regulation of CLCF1 and BTLA expression, and ZNF384 fusion proteins consistently showed higher activity to promote transcription of these target genes relative to wild-type ZNF384 in vitro. Ectopic expression of EP300-ZNF384 and CREBBP-ZNF384 fusion altered differentiation of mouse hematopoietic stem and progenitor cells and also potentiated oncogenic transformation in vitro. EP300- and CREBBP-ZNF384 fusions resulted in loss of histone lysine acetyltransferase activity in a dominant-negative fashion, with concomitant global reduction of histone acetylation and increased sensitivity of leukemia cells to histone deacetylase inhibitors. In conclusion, our results indicate that gene fusion is a common class of genomic abnormalities in childhood ALL and that recurrent translocations involving EP300 and CREBBP may cause epigenetic deregulation with potential for therapeutic targeting.