Transcriptional regulations by the Tip60/p400/H2A.Z complex in the intestinal epithelial physiopathology
(M. Briet & F. Escaffit)

Project managers : Martine BRIET & Fabrice ESCAFFIT

Chromatin modifying enzymes are involved in the control of most of the major cellular processes (transcription, DNA repair, proliferation, apoptosis, ...), via the regulation of the expression of numerous proteins by acting as co-activators or co-repressors within transcriptional complexes. These complexes may include transcription factors that participate in their targeting to specific promoters. These enzymes induce chromatin modifications (e.g. DNA methylation or post-translational modifications of histones) that modulate its compaction and modify the accessibility of promoters to transcription factors and transcriptional machinery. 

This phenomenon allows the establishment of specialized genetic programs during development, but also the dynamic response of the cell to the conditions of its environment, and particularly the response to stress. The alteration of these capacities is implicated in a large number of pathologies, notably tumors or degenerative diseases. Thus, it is crucial to understand its impact and its contribution to human physiopathology. The projects we are conducting are therefore aimed at studying the role of chromatin and the complexes ensuring its remodeling in :

• the induction of differentiation processes
• the control of cell proliferation and survival
• genetic stability

In this context, we are interested in chromatin mechanisms, including post-translational modifications of histones or incorporation of canonical histone variants, in the maintenance of homeostasis and gut function. 
Thus, we are particularly interested in the Tip60/p400/H2A.Z enzymatic complex, which is involved in these chromatin regulations and which presents, among others, a histone acetyltransferase activity, carried by the Tip60 protein, as well as a histone exchange activity, ensured by the ATPase p400 which participates in the incorporation of the histone variant H2A.Z. We have demonstrated the crucial role of the balance between these 2 proteins in the progression of colorectal cancers (Mattera et al., 2009), via the control of the response to cellular stresses (oxidative, oncogenic, ...) (Mattera et al., 2010) and of a key signaling pathway for this progression: the Wnt pathway (Chevillard-Briet et al., 2014).

The Wnt pathway, strongly involved in tumorigenesis, plays above all a major role in the development and homeostasis of the intestinal epithelium via, in particular, the renewal of stem cells and the spatio-temporal control of differentiation. We observed that the H2A.Z variant plays a crucial role in the proliferation of intestinal epithelial cells in culture as well as in the expression of differentiation markers in vitro and in vivo in mice (Rispal et al., 2019). This is in agreement with the decreased expression of H2A.Z that is observed during intestinal epithelial differentiation (Kazakevych et al., 2017). 

Incorporated into chromatin through p400 and acetylated by Tip60 which changes its function, the histone variant H2A.Z is encoded by 2 different genes H2AFZ and H2AFV from which 3 different isoforms are expressed: the first two, H2A.Z1 and H2A.Z2, differ from each other by only 3 amino acids. The third one, splice variant of H2A.Z2 (called H2A.Z2.2), confers a very particular dynamics to the nucleosome and thus significantly affects the properties of the chromatin. These isoforms, notably H2A.Z1 and H2A.Z2, seem to have a well-controlled spatial and temporal regulation and exert partially non-redundant functions. Indeed, it has been shown that their expressions vary during development and between different organs, and that their functions can be different in physiological or pathological situations.

Our recent work shows that each of these isoforms plays a well-defined role in both stem cell maintenance and in the maturation of the intestinal epithelium, including the establishment of mature cell lineages (Rispal et al., submitted). Thus, we observed that reduction of H2A.Z1 expression or overexpression of H2A.Z2 resulted in a net increase in markers of enterocyte differentiation, such as sucrase-isomaltase. This suggests that H2A.Z isoforms are differentially involved in cell fate and intestinal epithelial maturation, and it is of particular interest to study the mechanisms underlying their involvement in tissue homeostasis, including enterocyte differentiation.

Project funded by:
La Ligue Nationale contre le Cancer, la Fondation ARC, l’ANR, l’INCA, la Fondation de France et le Cancéropôle GSO

Publications on the subject (the team members are in bold):

Rispal J, Escaffit F. and Trouche D. (2020) Chromatin dynamics in intestinal epithelial homeostasis: a paradigm of cell fate determination versus cell plasticity. Stem Cell Rev Rep. 16 (6): 1062-80. Abstract

Rispal J, Baron L, Beaulieu J-F, Chevillard-Briet M, Trouche D and Escaffit F. (2019) The H2A.Z histone variant integrates Wnt signaling in intestinal epithelial homeostasis. Nature Communications. 10 (1): 1827-35. Abstract

Chevillard-Briet, M. and Escaffit, F. (2018) Methods for In Vivo Functional Studies of Chromatin-Modifying Enzymes in Early Steps of Colon Carcinogenesis. In: Colorectal Cancer. Methods in Molecular Biology - Beaulieu JF (eds), Humana Press, New York, NY 1765:79-85. Abstract

Grézy, A., Chevillard-Briet, M., Trouche, D. and Escaffit, F. (2016) Control of genetic stability by a new heterochromatin compaction pathway involving the Tip60 histone acetyltransferase. Mol Biol Cell 27(4):599-607. Abstract

Chevillard-Briet, M., Quaranta, M., Grézy, A., Matterra, L., Courilleau, C., Philippe, M., Mercier, P., Corpet, D., Lough, J., Ueda, T., Fukunaga, R., *Trouche, D. and *Escaffit, F. (*co-last authors). (2014) Interplay between chromatin modifying enzymes controls colon cancer progression through Wnt signaling. Human Mol Genet 23: 2120-31. Abstract .

*Mattera, L., *Courilleau, C. (*co-first authors), Legube, G., Ueda, T., Fukunaga, R., Chevillard-Briet, M., §Canitrot, Y., §Escaffit, F. (§ equal contribution), Trouche, D. (2010) The E1A-associated p400 protein modulates cell fate decision by the regulation of ROS homeostasis. PLoS Genet., 6(6):e1000983. Abstract .

*Mattera, L., *Escaffit, F. (*co-first authors), Pillaire, M.-J., Selves, J., Tyteca, S., Hoffmann, J.-S., Gourraud, P.-A., §Chevillard-Briet, M., §Cazaux, C. (§ equal contribution), Trouche, D. (2009) The p400/Tip60 ratio is critical for colorectal cancer cells proliferation through DNA damage response pathways. Oncogene. 28(12):1506-17. Abstract

Funding