Cells must maintain some genes in a silent state while keeping them poised for later expression. This property is critical for memory lymphocytes. We found that a transcription factor, Oct1, plays a major role in poising interleukin-2 (Il2) in T cells. Our findings indicate that Oct1 regulates target gene transcription through two mutually exclusive mechanisms involving different chromatin modifying complexes: as a repressor through association with NuRD, and as an activator (more accurately, anti-repressor) through association with a histone demethylase known as Jmjd1a. Oct1 can switch from one mode to the other, even at the same gene, in response to ERK signaling. In resting but previously stimulated T cells, Oct1 uses Jmjd1a to prevent the accumulation of negative epigenetic marks and stable repression, thus poising Il2 for the more rapid and stronger induction associated with secondary stimulation. Oct1 is also critical for maintaining CD4 memory T cell numbers and function. This proposal will determine 1) how Oct1 switching to anti-repression is established and maintained in T cells, using Il2 as a model target, 2) whether Oct1 regulates multiple target genes in the same manner, and 3) the physiological consequences. Our central hypothesis is that Oct1 prevents stable repression of multiple targets, to help maintain a poised transcriptional state associated with memory. Success with these experiments will eliminate the confusion surrounding the role of Oct1 in the regulation of these genes, and identify a mechanism by which memory T cells maintain critical genes in poised epigenetic states for later expression. We propose three aims:
Specific Aim 1 : Determine the mechanism underlying Oct1 switching from a pro- repressive to a pro-poising state.
Specific Aim 2 : Identify the target genes that utilize Oct1 to prevent repression.
Specific Aim 3 : Determine the functional consequences of Oct1 anti-repression.
The project is most relevant to the system we rely on: T cell memory. The three most exiting aspects of this work are: 1) the potential to uncover a previously unappreciated cardinal element in the regulation of CD4 T cell memory responses, and the mechanism. 2) The potential to identify a widespread new mode of gene regulation of genes such as Il2 by the transcription factor, Oct1. 3) The potential to explain much of the conflicting literature with respect to Oct1 (and possibly also Oct2), whose function in the immune system remains unclear in many respects. Therefore, we feel that this proposal has a strong possibility of moving the field forward.
