PubMed Health⌕ Search

Biomedical subjects

David F Callen

Publications and source records attributed to David F Callen.

10 recordsLinked to original sources
PubMed2006

ZNF652, a novel zinc finger protein, interacts with the putative breast tumor suppressor CBFA2T3 to repress transcription.

The transcriptional repressor CBFA2T3 is a putative breast tumor suppressor. To define the role of CBFA2T3, we used a segment of this protein as bait in a yeast two-hybrid screen and identified a novel uncharacterized protein, ZNF652. In general, primary tumors and cancer cell lines showed lower expression of ZNF652 than normal tissues. Together with the location of this gene on the long arm of chromosome 17q, a region of frequent loss of heterozygosity in cancer, these results suggest a possible role of ZNF652 in tumorigenesis. In silico analysis of this protein revealed that it contains multiple classic zinc finger domains that are predicted to bind DNA. Coimmunoprecipitation assays showed that ZNF652 strongly interacts with CBFA2T3 and this interaction occurs through the COOH-terminal 109 amino acids of ZNF652. In contrast, there was a weak interaction of ZNF652 with CBFA2T1 and CBFA2T2, the other two members of this ETO family. Transcriptional reporter assays further confirmed the strength and selectivity of the ZNF652-CBFA2T3 interaction. The transcriptional repression of growth factor independent-1 (GFI-1), a previously characterized ETO effector zinc finger protein, was shown to be enhanced by CBFA2T1, but to a lesser extent by CBFA2T2 and CBFA2T3. We therefore suggest that each of the various gene effector zinc finger proteins may specifically interact with one or more of the ETO proteins to generate a defined range of transcriptional repressor complexes.

Amino Acid Sequence↗
PubMed2005

FBXO31 is the chromosome 16q24.3 senescence gene, a candidate breast tumor suppressor, and a component of an SCF complex.

A BAC located in the 16q24.3 breast cancer loss of heterozygosity region was previously shown to restore cellular senescence when transferred into breast tumor cell lines. We have shown that FBXO31, although located just distal to this BAC, can induce cellular senescence in the breast cancer cell line MCF-7 and is the likely candidate senescence gene. FBXO31 has properties consistent with a tumor suppressor, because ectopic expression of FBXO31 in two breast cancer cell lines inhibited colony growth on plastic and inhibited cell proliferation in the MCF-7 cell line. In addition, compared with the relative expression in normal breast, levels of FBXO31 were down-regulated in breast tumor cell lines and primary tumors. FBXO31 was cell cycle regulated in the breast cell lines MCF-10A and SKBR3 with maximal expression from late G(2) to early G(1) phase. Ectopic expression of FBXO31 in the breast cancer cell line MDA-MB-468 resulted in the accumulation of cells at the G(1) phase of the cell cycle. FBXO31 contains an F-box domain and is associated with the proteins Skp1, Roc-1, and Cullin-1, suggesting that FBXO31 is a component of a SCF ubiquitination complex. We propose that FBXO31 functions as a tumor suppressor by generating SCF(FBXO31) complexes that target particular substrates, critical for the normal execution of the cell cycle, for ubiquitination and subsequent degradation.

Blotting, Northern↗
PubMed2004

The sequence and analysis of duplication-rich human chromosome 16.

Human chromosome 16 features one of the highest levels of segmentally duplicated sequence among the human autosomes. We report here the 78,884,754 base pairs of finished chromosome 16 sequence, representing over 99.9% of its euchromatin. Manual annotation revealed 880 protein-coding genes confirmed by 1,670 aligned transcripts, 19 transfer RNA genes, 341 pseudogenes and three RNA pseudogenes. These genes include metallothionein, cadherin and iroquois gene families, as well as the disease genes for polycystic kidney disease and acute myelomonocytic leukaemia. Several large-scale structural polymorphisms spanning hundreds of kilobase pairs were identified and result in gene content differences among humans. Whereas the segmental duplications of chromosome 16 are enriched in the relatively gene-poor pericentromere of the p arm, some are involved in recent gene duplication and conversion events that are likely to have had an impact on the evolution of primates and human disease susceptibility.

Animals↗
PubMed2004

Aberrant CBFA2T3B gene promoter methylation in breast tumors.

BACKGROUND: The CBFA2T3 locus located on the human chromosome region 16q24.3 is frequently deleted in breast tumors. CBFA2T3 gene expression levels are aberrant in breast tumor cell lines and the CBFA2T3B isoform is a potential tumor suppressor gene. In the absence of identified mutations to further support a role for this gene in tumorigenesis, we explored whether the CBFA2T3B promoter region is aberrantly methylated and whether this correlates with expression. RESULTS: Aberrant hypo and hypermethylation of the CBFA2T3B promoter was detected in breast tumor cell lines and primary breast tumor samples relative to methylation index interquartile ranges in normal breast counterpart and normal whole blood samples. A statistically significant inverse correlation between aberrant CBFA2T3B promoter methylation and gene expression was established. CONCLUSION: CBFA2T3B is a potential breast tumor suppressor gene affected by aberrant promoter methylation and gene expression. The methylation levels were quantitated using a second-round real-time methylation-specific PCR assay. The detection of both hypo and hypermethylation is a technicality regarding the methylation methodology.

Breast Neoplasms↗
PubMed2004

The de novo chromosome 16 translocations of two patients with abnormal phenotypes (mental retardation and epilepsy) disrupt the A2BP1 gene.

The 16p13.3 breakpoints of two de novo translocations of chromosome 16, t(1;16) and t(14;16), were shown by initial mapping studies to have physically adjacent breakpoints. The translocations were ascertained in patients with abnormal phenotypes characterized by predominant epilepsy in one patient and mental retardation in the other. Distamycin/DAPI banding showed that the chromosome 1 breakpoint of the t(1;16) was in the pericentric heterochromatin therefore restricting potential gene disruption to the 16p13.3 breakpoint. The breakpoints of the two translocations were localized to a region of 3.5 and 115 kb respectively and were approximately 900 kb apart. The mapping was confirmed by fluorescence in situ hybridization (FISH) of clones that spanned the breakpoints to metaphase spreads derived from the patients. The mapping data showed both translocations disrupted the ataxin-2-binding protein 1 ( A2BP1) gene that encompasses a large genomic region of 1.7 Mb. A2BP1 encodes a protein that is known to interact with the spinocerebellar ataxia type 2 ( SCA2) protein. It is proposed that disruption of the A2BP1 gene is a cause of the abnormal phenotype of the two patients. Ninety-six patients with sporadic epilepsy and 96 female patients with mental retardation were screened by SSCP for potential mutations of A2BP1. No mutations were found, suggesting that disruption of the A2BP1 gene is not a common cause of sporadic epilepsy or mental retardation.

Adolescent↗
PubMed2002

CBFA2T3 (MTG16) is a putative breast tumor suppressor gene from the breast cancer loss of heterozygosity region at 16q24.3.

Numerous cytogenetic and molecular studies of breast cancer have identified frequent loss of heterozygosity (LOH) of the long arm of human chromosome 16. On the basis of these data, the likely locations of breast cancer tumor suppressor genes are bands 16q22.1 and 16q24.3. We have mapped the CBFA2T3 (MTG16) gene, previously cloned as a fusion partner of the AML1 protein from a rare (16;21) leukemia translocation, to the 16q24.3 breast cancer LOH region. The expression of CBFA2T3 was significantly reduced in a number of breast cancer cell lines and in primary breast tumors, including early ductal carcinomas in situ, when compared with nontransformed breast epithelial cell lines and normal breast tissue. Reintroduction of CBFA2T3 into different breast tumor derived cell lines with decreased expression of this gene reduced colony growth on plastic and in soft agar. CBFA2T3 was shown to function as a transcriptional repressor when tethered to the GAL4 DNA-binding domain in a reporter gene assay and, therefore, has the potential to be a transcriptional repressor in normal breast epithelial cells. Taken together, these findings suggest that CBFA2T3 is a likely candidate for the breast cancer tumor suppressor gene that is the target for the frequent 16q24 LOH in breast neoplasms.

Breast Neoplasms↗
PubMed2002

Study of 250 children with idiopathic mental retardation reveals nine cryptic and diverse subtelomeric chromosome anomalies.

Cryptic subtelomeric chromosome anomalies have been recognized as a significant cause of dysmorphology and mental retardation. To determine whether the clinical cytogenetics laboratory should screen routinely for these aberrations, we have tested 250 patients with idiopathic mental retardation/developmental delay, either isolated (53) or associated with dysmorphic features and/or malformations in the absence of a recognizable syndrome (197). All had normal karyotypes at the 550-850 band level. Subtelomeric anomalies were found in 1/53 of the first group (1.9%) and 8/197 of the second group (4.1%). In one patient, two separate anomalies were present: a deletion (not inherited) and a duplication (inherited). It is possible that one of these 10 observed aberrations might represent a rare and previously unreported polymorphism and one a rare cross-hybridization. Our study supports the proposition that cryptic subtelomeric rearrangements are a significant cause of idiopathic mental retardation/developmental delay, but both the diversity of the phenotypes of the positive cases and the wide diversity of their associated chromosome abnormalities emphasize the central problem for the clinical cytogenetics laboratory-that of choosing the most productive patient base for this useful diagnostic test.

Adolescent↗
PubMed2002

Sequencing, transcript identification, and quantitative gene expression profiling in the breast cancer loss of heterozygosity region 16q24.3 reveal three potential tumor-suppressor genes.

Loss of heterozygosity (LOH) of chromosome 16q24.3 is a common genetic alteration observed in invasive ductal and lobular breast carcinomas. We constructed a physical map and generated genomic DNA sequence data spanning 2.4 Mb in this region. Detailed in silico and in vitro analyses of the genomic sequence data enabled the identification of 104 genes. It was hypothesized that tumor-suppressor genes would exhibit marked mRNA expression variability in a panel of breast cancer cell lines as a result of downregulation due to mutation or hypermethylation. We examined the mRNA expression profiles of the genes identified at 16q24.3 in normal breast, a normal breast epithelial cell line, and several breast cancer cell lines exhibiting 16q24.3 LOH. Three of the genes, CYBA, Hs.7970, and CBFA2T3, exhibited variability ten times higher than the baseline. The possible role of these genes as tumor suppressors is discussed.

Breast Neoplasms↗
PubMed2002

Defining regions of loss of heterozygosity of 16q in breast cancer cell lines.

The loss of heterozygosity (LOH) of chromosome 16 was assessed in 21 breast cancer cell lines and two nontumorigenic breast epithelial cell lines by typing microsatellite markers distributed on this chromosome. In addition, dual-color fluorescence in situ hybridization was used to metaphase spreads of these cell lines using chromosome 16 paint and region specific probes. Eleven of the cell lines had LOH for chromosome 16, two for the entire chromosome, three for the long arm, and six had LOH for restricted regions of the long arm. The results supported evidence that there are two predominant regions of LOH, 16q22.1 and 16q24.3. The cell lines with chromosome 16 LOH can be used for screening candidate tumor suppressor genes at 16q in breast cancer.

Breast Neoplasms↗