N-myc transactivates RCC1 gene expression in rat fibroblast cells transformed by N-myc and v-ras.
Oncogenic cooperation was found between the N-myc and v-ras oncogenes in a rat fibroblast cell line, 3Y1. To investigate the specific role of N-myc in the transformation, we established transformed cell lines that expressed N-myc under a controllable promoter. Using these cells, we found that constitutive expression of N-myc is necessary to maintain the transformation, and that the expression level of N-myc is closely correlated with the transformation. Since another myc family gene, c-myc, directly activates expression of RCC1, which has important functions for eukaryotic cell proliferation, we focused on the relationship between N-myc and RCC1. Cells transformed by N-myc and v-ras expressed several times more RCC1 mRNA than the parent 3Y1 cells, and the expression of RCC1 changed in a parallel with the expression of N-myc. Gel retardation analysis and experiments with reporter plasmids constructed from a DNA fragment of the RCC1 gene indicated that the N-Myc protein controls expression of RCC1 by binding directly to CACGTG elements in the RCC1 gene. These results suggest that N-myc can directly transactivate expression of RCC1, a c-myc target gene.
Tsuneoka
M
M
Institute of Life Science, Kurume University, Kurume, Fukuoka, 839-0861, Japan. tsuneoka@mbox.lsi.kurume-u.ac.jp
Mekada
E
E
D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D015689:Oncogene Protein p21(ras) / Q000502:physiology*; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D015533:Transcriptional Activation / Q000502:physiology*
D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D015689:Oncogene Protein p21(ras)