Interferon and growth factor modulation of nuclear factors binding to 5' upstream elements of the 2-5A synthetase gene

The murine p202 protein, an IFN-inducible modulator of transcription, is activated by the mitogen platelet-derived growth factor

p202 is a murine interferon (IFN)-inducible protein belonging to a cluster of IFN-inducible genes (the 200 family) located in a segment of chromosome 1. It is a nuclear DNA-binding protein that is able to modulate transcription by interacting with a heterogeneous set of transcription factors, including NF-kappaB, (p50/p65), AP-1, c-fos, c-jun, and RB-1. The p202 protein is believed to attenuate cell growth/proliferation, mainly through the activation of IFN-stimulated of gene factor 3 (ISGF3), which binds IFN-stimulated response elements (ISRE) located in the promoters of type I IFN genes. In this report, we show that the p202 gene can also be induced by platelet-derived growth factor (PDGF), a mitogen known to drive G(0)-arrested cells toward reentry into the cell cycle. PDGF transiently enhances the steady-state mRNA level of p202 and increases the p202 protein level independently from IFN signaling, by acting at the transcriptional level on its promoter. The kinetics of p202 induction by PDGF are faster and more transient than those of IFN. These data identify p202 as a member of the IFN-inducible gene family that can be directly regulated by mitogenic stimuli.

Sequence-specific DNA-binding proteins within the Mbcr on the Ph1 chromosome

The Philadelphia1 (Ph1) chromosome results from a reciprocal translocation between chromosome 9 and chromosome 22, which fuses a portion of the ABL oncogene to the BCR gene, forming the BCR/ABL fusion gene. This produces a fusion protein with a greatly increased protein tyrosine kinase activity in comparison to that of the normal ABL protein. The BCR/ABL gene is transcribed from the promoter of the normal BCR gene, but little is known about the regulation of its expression. In this study, we asked whether there are sequence-specific DNA-binding proteins (DBP) that bind to the breakpoint cluster region (bcr, or Mbcr) within the BCR gene. Sequence-specific DBP located within the Mbcr could have a transcription-regulating effect, and they could participate in the recombination that generates BCR/ABL. Our data show that there are sequence-specific DBP that bind within the Mbcr.