Analysis of location and integrity of the human PITSLRE (p58(cdc2L1)) genes in neuroblastoma cell genomes.

The family of PITSLRE kinase genes, located in chromosome 1p36, has recently been associated with neuroblastoma tumorigenesis. In order to evaluate the role of these genes as putative tumor suppressor genes, we have analyzed the integrity of the coding region in primary tumors and its location relative to a neuroblastoma consensus deletion. A subset of aggressive neuroblastoma tumors with allelic loss of different parts of chromosome 1p were investigated. Single-strand conformation polymorphism (SSCP), heteroduplex (HD) and sequencing analysis of tumor DNA did not reveal any significant changes in the coding region. In particular, a primary tumor with an interstitial allelic deletion in 1p36 did not reveal concomitant loss of heterozygosity of the PITSLRE gene region when analyzed with a C/T DNA sequence polymorphism in exon 5 of PITSLRE1. FISH analysis on neuroblastoma cell lines with small interstitial deletions and with a balanced translocation in 1p36 revealed that the PITSLRE gene cluster was localized distal to the neuroblastoma consensus deletion. against an involvement of the PITSLRE genes in neuroblastoma tumorigenesis.

Molecular cloning and expression analysis of five novel genes in chromosome 1p36.

The human chromosome 1p36 region displays frequent nonrandom chromosomal deletions and translocations in a number of human malignancies; these are thought to inactivate tumor suppressor genes. To identify these putative tumor suppressors we employed exon trapping, cDNA selection, and zoo blot analysis to clone five new genes located in 1p36. Two of these represent novel genes and were designated C1orf1 and xylan 1,4-beta-xylosidase 1 (XBX1). Two further genes represented new members of known gene families: PTPRZ2 was a tyrosine phosphatase and FRAP2 represented a FKBP12-rapamycin-associated protein. The fifth gene identified, ENO1L1, was significantly homologous to c-myc promoter binding protein, MBP-1, and to enolase 1 (ENO1). It colocalized with alpha enolase (ENO1) on a single P1 clone. ENO1L1 differed from both ENO1 and MBP-1 in the organization of its 5' untranslated sequences. Second, MBP-1 contained two single-base insertions not present in either ENO1 or ENO1L1 sequences, which led to a shift in the MBP-1 reading frame. Expression analysis revealed two brain-specific transcripts of 7.9 and 6.5 kb for PTPRZ2. In contrast, C1orf1, FRAP2, ENO1L1, and XBX1 appeared to be expressed ubiquitously in the tissues tested, with transcript sizes of 4.5, 8.7, 1.75, and 4.5 kb, respectively. Using fluorescence in situ hybridization, we mapped the five novel genes relative to chromosome 1p36 breakpoints present in three established tumor cell lines and one nontumor cell line. The karyotypic abnormalities in these cell lines were exploited as chromosomal landmarks; we could thus show that the telomere to centromere gene order was PTPRZ2-(MBP-1/ENO1/ENO1L1)-(C1orf1/XBX1)-+ ++FRAP2. The localization of these genes to a chromosomal region that is prone to deletions in human cancers makes them potential candidate tumor suppressors.

Human RERE is localized to nuclear promyelocytic leukemia oncogenic domains and enhances apoptosis.

RE repeats encoded (RERE) was identified recently as a protein with high homology to the atrophin-1 protein, which appears to be causal in the hereditary neurodegenerative disorder termed dentatorubral-pallidoluysian atrophy (DRPLA) caused by an abnormal glutamine expansion. We have independently identified RERE in a search for genes localized to the translocation breakpoint region at chromosome 1p36.2 in the neuroblastoma cell line NGP. Here we show that neuroblastoma tumor cell lines display reduced abundance of RERE transcripts. Furthermore, we detected RERE protein mainly in the nucleus, where it colocalizes with the promyelocytic leukemia protein in promyelocytic leukemia oncogenic domains (PODs). Overexpression of RERE recruits a fraction of the proapoptotic protein BAX to PODS: This observation correlates with RERE-induced apoptosis, which occurs in a caspase-dependent manner. These results identify RERE as a novel component of PODs and suggest an important role of RERE in the control of cell survival.

TEL is a sequence-specific transcriptional repressor.

TEL is a gene frequently involved in specific chromosomal translocations in human leukemia and sarcoma that encodes a member of the ETS family of transcriptional regulators. TEL is unusual among other ETS proteins by its ability to self-associate in vivo, a property that is essential to the oncogenic activation of TEL-derived fusion proteins. We show here that TEL is a sequence-specific transcriptional repressor of ETS-binding site-driven transcription of model and natural promoters. Deletion of the oligomerization domain of TEL or its substitution by the homologous region of monomeric ETS1 impaired the ability of TEL to repress. In contrast, substitution of the oligomerization domain of TEL by unrelated oligomerization domains resulted in an active repressor, showing that the ability of TEL to repress depends on its ability to self-associate. The study of the properties of TEL fusions to the heterologous DNA binding domain of Gal4 identified two autonomous repression domains in TEL, distinct from its oligomerization domain, that are essential to the ability of TEL to repress ETS-binding site-containing promoters. These results have implications for the normal function of TEL, its relation to other ETS proteins, and its role in leukemogenesis.