Identification and characterization of a new gene physically linked to the ATM gene.

Abstract

Ataxia telangiectasia [AT} is an autosomal recessive disease of unknown etiology associated with cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, and hypersensitivity to ionizing radiation. Although AT has been divided into four complementation groups by its radioresistant-DNA synthesis phenotype, the ATM gene has been isolated as the candidate gene responsible for all AT groups. We identified a new gene, designated NPAT, from the major AT locus on human chromosome Ilq22-q23. The gene encoded a 1421-amino-acid protein containing nuclear localization signals and phosphorylation target sites by cyclin-dependent protein kinases associated with E2F. The messenger RNA of NPAT was detected in all human tissues examined, and its genomic sequence was strongly conserved through eukaryotes, suggesting that the NPAT gene may be essential for cell maintenance and may be a member of the housekeeping genes. Analysis of the genomic region of NPAT surprisingly revealed that the gene existed only 0.5 kb apart from the 5' end of the ATM transcript with opposite transcriptional direction, it may be possible to propose the idea that the promoter region could be shared by both housekeeping genes and that each gene could influence the expression of the other.

Aberrant methylation of the ATM promoter correlates with increased radiosensitivity in a human colorectal tumor cell line

“…To explain the dramatically reduced level of ATM in our HCT-166 cells, we hypothesized that expression of the ATM gene was silenced via aberrant promoter methylation because the proximal promoter of the ATM gene is located within a CpG island (Byrd et al, 1996;Imai et al, 1996). To test this, we exposed cultures of HCT-116 cells to two sequential doses of the global demethylating agent 5-azacytidine as previously outlined (Veigl et al, 1998).…”

“…The ATM and NPAT genes share a common *520 bp intergenic region located on human chromosome 11, region q22-23 (Byrd et al, 1996;Imai et al, 1996). Based on the location of this segment between the two genes that run in opposite orientation, and supported by reporter assays that show that both orientations of this region promote transcription in vivo, it has been proposed that this intergenic interval is a bi-directional promoter (Byrd et al, 1996).…”

“…The putative proximal promoter of the ATM gene is a *520 bp region shared with the NPAT/E14/CAND3 gene (Byrd et al, 1996;Imai et al, 1996;Chen et al, 1997). Owing to the placement of this region between two genes transcribed in opposite orientation, and supported by reporter assays, it has been proposed that this sequence is a bi-directional promoter (Byrd et al, 1996).…”

Expression of NPAT, a novel substrate of cyclin E-CDK2, promotes S-phase entry

“…Therefore, this clone was chosen for further studies. While our work was in progress, the gene was also isolated independently, under the names NPAT, E14, and CAN3, through positional cloning by virtue of the fact that the gene is located next to ATM on chromosome 11q22-q23 and may share a bidirectional promoter with ATM (Byrd et al 1996;Imai et al 1996;Chen et al 1997).…”

X‐Irradiation Induces Up‐regulation of ATM Gene Expression in Wild‐type Lymphoblastoid Cell Lines, but Not in Their Heterozygous or Homozygous Ataxia‐telangiectasia Counterparts

“…Thus, for example, the ATM sequence is organized in head-to-head configuration with the sequence of a second gene, NPAT/E14/CAND3, with which it shares a bi-directional promoter that contains CCAAT boxes and 4 consensus sites for the Sp1 transcription factor and whose transcription start site is only 550 base pairs away from the ATM start site. [28][29][30] Sp1 is a candidate factor for common regulation of the activities of these two genes. Additional evidence that may be of some relevance includes a recent report by Gueven et al 31) which indicates that epidermal growth factor (EGF) increases radiosensitivity in both human fibroblasts and lymphoblasts and that this is associated with a controlled down-regulation of ATM.…”