An amino-terminal domain of Mxi1 mediates anti-Myc oncogenic activity and interacts with a homolog of the yeast transcriptional repressor SIN3

Effects of the MYC oncogene antagonist, MAD, on proliferation, cell cycling and the malignant phenotype of human brain tumour cells

To investigate how overexpression of MAD, an antagonist of MYC oncogenes influences the malignant phenotype of human cancer cells, an adenovirus vector system was used to transfer the human MAD gene (AdMAD) into human astrocytoma cells. Decreased growth potential of AdMAD-infected cells was evidenced by a decrease in [3H]thymidine incorporation, an increase in cell doubling time and alteration of cell-cycle distribution. Diminished malignant potential of AdMAD-infected cells was manifested by their loss of anchorage-independent growth in soft agar and by their inability, in general, to induce tumorigenesis in a xenograft animal model. These studies indicate that adenovirus constructs encoding MAD dramatically inhibit the proliferation and tumorigenicity of human astrocytoma cells and support the use of MAD for gene therapy of human tumours.

SIN3 works through two different promoter elements to regulate INO1 gene expression in yeast

The SIN3 global regulatory factor affects expression of many yeast genes, including the phospholipid biosynthetic gene, INO1. Mutations in the SIN3 gene result in elevated levels of INO1 expression under conditions that normally confer full repression of INO1 transcription, indicating that SIN3 is a negative regulator of INO1. In this study, the INO1 promoter was analyzed for sequences that play a role in responding to SIN3-mediated repression. Two distinct promoter elements, the upstream repression sequence (URS1) and the INO1 upstream activation sequence (UASINO) both were found to be involved in enabling SIN3 to repress INO1 expression.