Michael D. Cole - US grants

DESCRIPTION (provided by applicant): We are interested in determining the function of the c-myc proto-oncogene in normal cells and how misregulation or overexpression of the c-Myc protein can induce cell transformation. Functional studies have demonstrated that a segment from the N-terminus of Myc (called Myc homology box II or MBII) is essential for oncogenic transformation. In the last granting period, we were able to purify and characterize a nuclear cofactor, called TRRAP, for TRansformation/tRansactivation Associated Protein, that binds to Myc through MBII. The discovery of TRRAP has proven to be a seminal discovery in the Myc field because it provided a link between Myc and chromatin modifying complexes that acetylate histones. Localized histone acetylation has been shown both biochemically and genetically to facilitate gene activation. This project will address the functional consequences of TRRAP complex recruitment by c-Myc. We will also explore the more global function of TRRAP itself and the growing number of TRRAP containing nuclear complexes. The specific aims are as follows: 1) We will characterize the structure and function of DNA Methyltransferase Associated Protein (DMAP1), a newly discovered protein associated with both Myc and TRRAP. We will test the hypothesis that DMAP1 is a critical Myc-associated histone acetyltransferase. 2) We will explore the function of the nuclear actin-related protein BAF53 and its role in chromatin modifying complexes. Specifically, we will determine the biochemical basis for the dominant inhibitory activity of a BAF53 mutant protein with a small deletion in a critical functional domain. 3) We will explore the function of the Enhancer of polycomb protein, which marks a unique set of HAT complexes. We will try to determine how complexes between TRRAP and Epc1 differ from those containing TRRAP and DMAP1, and we will examine the role of these complexes in gene regulation. 4) We will determine the role of individual HATs and cofactors in the activation of specific cellular target genes. The role of each protein in the activation of the silent TERT gene will be addressed. We will test for synergism between Myc and the Sp1 transcription factor in the activation of the silent telomerase reverse transcriptase (TERT) gene.

DESCRIPTION (provided by applicant): The c-myc gene is among the most frequent sites of mutation for any oncogene in human cancer. Approximately 15% of all cancers exhibit amplification of the c-myc gene and about 25% of breast cancers have similar mutations. Chromosomal translocations at c-myc occur in 100% of Burkitt's lymphomas, as well as in the related mouse plasmacytomas. In addition to these gross rearrangements, missense mutations can also play a major role in the oncogenic activity of c-myc, and more than 60% of Burkitt's and AIDS associated lymphomas have mutations that alter the protein structure of the already translocated c-myc gene. The major question confronting the c-myc field (and nuclear oncogenes in general) is which cellular genes are targeted by the oncoprotein to mediate its function in oncogenic transformation, cell cycle progression or apoptosis. Of broader interest is how the c-myc gene itself is regulated in response to diverse signaling pathways. The specific goals of this project are to: 1) Dissect the functional role of individual target genes in mediating the proliferative activity of the Myc transcription factor. Research will involve functional screens to discover specific genes that contribute directly to the Myc pathway. 2) Dissect the apoptotic, proliferative and oncogenic response of the Myc transcription factor using specific mutants that are defective in each biological activity using a dedicated Myc target gene microarray. 3) Use Drosophila genetics to gain insight into the regulatory pathways that govern c-myc gene expression, with particular emphasis on understanding the unique features of c-myc gene auto-suppression.

DESCRIPTION (provided by applicant): The c-MYC gene is among the most frequent sites of mutation for any oncogene in human cancer. Approximately 15% of all cancers exhibit amplification of the c-MYC gene and about 25% of breast cancers have similar mutations. Chromosomal translocations at c-MYC occur in 100% of Burkitt's lymphomas, as well as in the related mouse plasmacytomas. In addition to these gross rearrangements, missense mutations can also play a major role in the oncogenic activity of c-MYC, and more than 60% of Burkitt's and AIDS-associated lymphomas have mutations that alter the protein structure of the already translocated c-MYC gene. From a very different perspective, inherited Single Nucleotide Polymorphisms (SNPs) that predispose to various cancers have frequently been mapped within or near the c-MYC gene. Beyond these overt mutations and polymorphisms, it is estimated that up to 70% of all cancers overexpress c-MYC in response to disruptions in various signaling pathways such as Wnt. A major question confronting the cancer field is how these mutations and polymorphisms target c-MYC and its downstream cellular targets to mediate oncogenic transformation, cell cycle progression or apoptosis. Of broader interest is how the c-MYC gene itself is regulated in response to diverse oncogenic signaling pathways. The specific goals of this project are to: Aim 1: Characterize the missense mutations frequently found in the c-MYC protein in Burkitt's and AIDS-associated lymphomas. Our hypothesis is that these mutations cluster at sites that enhance oncogenic activity and dramatically shift the profiles of c-MYC target genes. Aim 2: Characterize the function of a novel direct target of c-MYC, the nol5a gene, that is hyperactivated by Burkitt's lymphoma associated c-MYC mutations. Our hypothesis is that the Nol5a protein potentiates c-MYC function through its role in ribosome biogenesis. Aim 3: Characterize the function of SNPs that map over a large domain on chromosome 8q24, a huge region (>2 Mb) that harbors only a single functional gene, i.e. c-MYC. Our hypothesis is that these SNPs map to very distal regulatory elements that control c-MYC gene expression in specific tissues and predispose (or protect) individuals from colon, prostate and breast cancer, dependent on the particular inherited allele. PUBLIC HEALTH RELEVANCE: Certain cellular genes are frequently mutated or misregulated to cause the abnormal growth of cancer cells. One of the most commonly mutated genes is called c-myc, and this gene is known to be an important regulatory of growth. The goal of the project is to understand how mutations change c-myc function in some cancers and how inherited variations near c-myc in the human genome can increase the risk of cancer.