Understand how the heme-oxidative stress pathway regulates gene expression by modulating the activity of intracellular transcriptional sensors

 

Recent pioneering studies revealed how heme signaling regulates a number of pathways, ranging from mitochondrial respiration to metabolism and circadian rhythms, by reversibly binding to and modulating the activity of “so-called” heme-sensor proteins. Heme-sensors participate in diverse biological processes including protein translation and transcription. In particular, it has been shown that binding of heme to transcriptional regulators switches on/off their activity and modulates the transcription of various enzymes and proteins that are critical to cellular physiology.

Despite these groundbreaking studies have provided critical data on how heme influences gene expression via regulation of transcriptional sensors, to date there is a limited understanding of the molecular events and machineries allowing signaling heme to modulate the cellular transcriptome.

To broaden our understanding of this biological process, our team focuses on:

 

1.  The mechanisms of regulation of the heme-sensor transcription factor BACH1. This transcriptional regulator is a major molecular link between the cellular heme levels, the redox state, and the transcriptional response. BACH1 functions both as a transcriptional repressor and activator, and regulates different biological processes like metabolism, cell growth, and cell cycle progression. Experimental evidence suggests that this pleiotropic transcriptional behavior is achieved by establishing different protein-protein networks with other transcriptional regulators that modulate its activity. However, to date, little is known about the specific transcriptional co-regulators working in conjunction with BACH1 to control certain transcriptional programs in response to heme fluctuations. Knowledge of these specific protein complexes is key to our understanding of how heme modulates BACH1 functions in physiology and of the mechanisms by which KEAP1/NRF2 mutant cancer cells rewire the transcriptional output of BACH1 to promote malignancy. To identify BACH1’s transcriptional co-regulators, we integrate results from standard immuno-purification purifications and BioID-based proximity labeling of BACH1 followed by mass spectrometry analysis. We anticipate that the results of this work will shed light on the mechanisms that control the transcriptional programs regulated by heme-BACH1, and is likely to uncover new mechanistic links between mutations in the KEAP1/NRF2 pathway in lung cancer and activation of pro-tumorigenic functions of BACH1.

 

2.  The identification of new heme-sensor transcription factors which may lead us to exploring uncharted biological fields. To discover these new regulators, we will combine proteomic and genetic strategies. Specifically, we will use proximity labeling approaches to identify transcriptional regulators interacting with heme. Moreover, we will integrate these analyses with genome-wide CRISPR screenings coupled with transcriptomic profiling techniques to identify the factors that implement the heme-controlled transcription.