DKC1 is an evolutionarily conserved c‐Myc target

Abstract

Objectives: We have identified dyskeratosis congenita 1 (DKC1) as a direct c-Myc transcriptional target in human cells. In these studies, we sought to determine if c-Myc-mediated DKC1 regulation is conserved across species. Methods: Murine p53-null colonocytes and Rat 1a fibroblasts, both expressing an inducible, c-Myc-estrogen receptor (MYC-ER) fusion protein, were incubated in media with 0.25% serum for 48 hrs; then stimulated with 250 nM 4-hydroxytamoxifen (4-OHT) for up to 72 hrs. At various time points, total RNA was harvested and Dkc1 levels were determined by quantitative RT-PCR. Telomerase reverse transcriptase (Tert), a known direct target of c-Myc; and vimentin (Vim) and β-actin, neither of which is regulated by c-Myc, served as controls for MYC-ER activation. All mRNA levels were normalized to β-actin expression. Results: Dkc1 was significantly upregulated in mouse (Figure 1) and rat cells following MYC-ER activation. A comparison between the human and mouse DKC1 genomic sequences revealed conservation of five c-Myc-binding E-box motifs within a region encompassing the promoter, exon 1 and intron 1. Through the use of chromatin immunoprecipitati on, we have previously demonstrated that endogenous c-Myc binds to these same sites in human cells, thus inferring a functional conservation. Conclusion: c-Myc-mediated DKC1 transcriptional regulation is not species or cell-type specific. Figure 1Open in figure viewerPowerPoint Dkcl expression is upregulated in MYC-ER mouse colonocytes