Immunology/ Gene Regulation

Malone Research Laboratory: Kim Vaccaro and Khachik Najaryan

Control of the on/off switch of an essential white blood cell-specific gene.

Overview:
The goal of this research project is to understand the control of a unique gene called B29.  B29 is a white blood cell-specific gene which when properly turned on allows white blood cells to develop into infectious disease-fighting cells.  When B29 is aberrantly turned off in white blood cells, these cells do not develop or function normally and may actually become leukemia cancer cells themselves. It is therefore absolutely essential for the B29 gene to be turned on in white blood cells and turned off in all other cell types. Understanding how B29 is turned on and off is now possible by the use of state-of-the-art molecular biology techniques.

Problem:
Precisely controlling when and where genes are turned on and off, known as controlling gene expression, is necessary for all cells to develop and function normally and avoid becoming cancerous or dying prematurely. This project focuses on how the expression of a white blood cell-specific gene called B29 is controlled. The B29 gene is absolutely required for the development and function of a type of white blood cell called a B cell in the immune system. Without the B29 gene, B cells do not develop and the immune system does not function properly to protect against infectious diseases. It is also essential that the B29 gene be turned off in all other cell types where its expression would impair the normal function of that cell.
The location of a gene on a chromosome generally determines the cell types in which that gene is turned on. For example, genes found within close proximity of each other are generally all turned on or all turned off in the same cell types1. The B29 gene, however, is located on a chromosome between several pituitary-specific genes including the growth hormone gene. The configuration of these genes in unusual because the B29 gene is only turned on in B cells and the pituitary-specific genes are only turned on in pituitary cells2.

This configuration where B29 is actually located between pituitary-specific genes suggests that they would all be turned on together in the same cell type. Since B29 is not turned on in pituitary cells where the surrounding pituitary-specific genes are turned on, the B29 gene must be switched on or off by a mechanism unique to this type of gene configuration. The availability of B cells and pituitary cells that grow in flasks of media in the laboratory makes our system ideal for studying the control of gene expression. Results gathered from our study will not only enhance the understanding of gene regulation at this particular locus, but will be applicable to many other gene configurations as well.

Our studies have identified two proteins potentially involved in the B29 gene on/off switch.  These two proteins, known as transcription factors, are called Oct-1 and Pit-1. The binding of transcription factors to DNA is known to play a role in turning genes on and off3. Oct-1 and Pit-1 have each have been shown in a test tube to bind to the segment of DNA we have evidence is the on/off switch for B29 gene expression4. We will use state-of-the-art molecular biology techniques to directly determine whether Oct-1 and Pit-1 bind to the potential B29 gene on/off switch on the chromosomes of living cells. We will also determine if activation and/or silencing is disturbed by blocking the binding of Oct-1 and Pit-1 to the on/off switch of B29.  Our results will provide support for the larger goal of determining exactly how these transcription factors actually switch on and off the B29 gene.

References Cited:
1. Fraser, P. and Grosveld, F. (1998). Current Opinion in Cell Biology, 10:361-365.
2. Patrone, L., Henson, S.E., Wall, R., and Malone, C.S. (2004). Molecular Biology Reports,   31:1-11.
3. Ogbourne, S. and Antalis, T.M. (1998).  Biochemical Journal, 331:1-14.
4. Malone, C.S., Fike, F.M., Teitell, M.A., and Wall, R. B29 (Igb, CD79b) gene silencing in pituitary cells is controlled by its 3' enhancer. Journal of Molecular Biology 362(2):173-183.

Grant Support

CSUN Research, Scholarship, and Creative Activity Award. “Control of the on/off switch of an essential white blood cell gene” (2006).