We study basic mechanisms of transcription and chromatin structure regulation in yeast and human cells. In yeast, we study the role of the Mediator complex, in the regulation of transcription pre-initiation complex assembly. Dysregulation of Mediator subunits is frequently associated with a variety of cancers, and it is our hope that our insights into the fundamental mechanisms of Mediator function gained in yeast will provide clues as to why misexpression of its subunits is so often observed in cancer. In human cells, we study the roles of the genome architecture factor CTCF, a tumor suppressor, and its paralog BORIS, a putative oncogene, in chromatin structure regulation. We have found that a phosphorylated form of CTCF is specifically retained on chromatin during mitosis, potentially serving as a bookmark for rapid reestablishment of proper chromatin structure and transcription after cell division. We hypothesize that defective CTCF bookmarking could lead to inappropriate transcriptional activation due to a lack of proper genomic structure, which could be carcinogenic. We are thus investigating the consequences of impairing CTCF mitotic retention on chromatin architecture and transcription. BORIS, the CTCF paralog, is normally only expressed in male germ cells but is activated in a number of cancer types. BORIS appears to act as a dominant-negative form of CTCF, potentially disrupting the normal CTCF-mediated genome architecture of somatic cells and activating a carcinogenic transcriptional program. We are thus analyzing the effects of BORIS overexpression on chromatin structure and transcription in a variety of human cell lines to better understand how its overexpression might promote cancer.
