Novel Interplay between p53 and HO-1 in Embryonic Stem Cells

Abstract

Stem cells genome safeguarding requires strict oxidative stress control. Heme oxygenase-1 (HO-1) and p53 are relevant components of the cellular defense system. p53 controls cellular response to multiple types of harmful stimulus, including oxidative stress. Otherwise, besides having a protective role, HO-1 is also involved in embryo development and in embryonic stem (ES) cells differentiation. Although both proteins have been extensively studied, little is known about their relationship in stem cells. The aim of this work is to explore HO-1-p53 interplay in ES cells. We studied HO-1 expression in p53 knockout (KO) ES cells and we found that they have higher HO-1 protein levels but similar HO-1 mRNA levels than the wild type (WT) ES cell line. Furthermore, cycloheximide treatment increased HO-1 abundance in p53 KO cells suggesting that p53 modulates HO-1 protein stability. Notably, H2O2 treatment did not induce HO-1 expression in p53 KO ES cells. Finally, SOD2 protein levels are also increased while Sod2 transcripts are not in KO cells, further suggesting that the p53 null phenotype is associated with a reinforcement of the antioxidant machinery. Our results demonstrate the existence of a connection between p53 and HO-1 in ES cells, highlighting the relationship between these stress defense pathways.

The pluripotency transcription factor OCT4 represses heme oxygenase‐1 gene expression

“…On the other hand, the increase in its expression during differentiation and our finding that it is repressed by OCT4, whose levels and function decrease along differentiation, reinforce the hypothesis that HO‐1 might be relevant for this process. We have previously performed a bioinformatic analysis with public data from high‐throughput microarrays and RNA‐sequencing experiments and found that HO‐1 mRNA levels increase in nondirected and in multiple different types of directed differentiation protocols; however, we have also found that HO‐1 mRNA levels decrease in differentiation directed to the endodermal lineage [62]. This is consistent with the fact that basal HO‐1 expression is high in some cellular types and low in others [62,63].…”

“…We have previously performed a bioinformatic analysis with public data from high‐throughput microarrays and RNA‐sequencing experiments and found that HO‐1 mRNA levels increase in nondirected and in multiple different types of directed differentiation protocols; however, we have also found that HO‐1 mRNA levels decrease in differentiation directed to the endodermal lineage [62]. This is consistent with the fact that basal HO‐1 expression is high in some cellular types and low in others [62,63]. It is worth mentioning that, in this work, we have analyzed an early time point of a nondirected differentiation protocol that displays a relatively homogeneous cell population in which there are no terminally differentiated cells yet.…”

“…OCT4 could be exerting its repressive effect on HO‐1 gene expression through interaction with other transcriptional regulators that affect chromatin architecture, such as histone and nucleic acid modifiers. Interestingly, analysis of public ChIP‐seq data sets showed that components of repressive complexes bind to Hmox1 locus in undifferentiated ES cells [62]. For example, we have found components of the polycomb repressive complex (PRC) like EZH2 and SUZ12 [65] and the components of the nuclear remodeling and histone deacetylation complex (NuRD) Chd4 and Mbd3 [66], among others.…”

“…For example, we have found components of the polycomb repressive complex (PRC) like EZH2 and SUZ12 [65] and the components of the nuclear remodeling and histone deacetylation complex (NuRD) Chd4 and Mbd3 [66], among others. Interestingly, we did not find these proteins bound to Hmox1 locus in data sets from ES cells subjected to differentiation protocols [62]. Moreover, we have found histone and DNA modifications typically associated with repressive chromatin, particularly H3K27me3, H3K4me1, and 5‐mC, in undifferentiated ES cells, and permissive marks, specifically H3K4me3 and H3K27Ac, in stem cells that have been subjected to differentiation [62].…”

“…Interestingly, we did not find these proteins bound to Hmox1 locus in data sets from ES cells subjected to differentiation protocols [62]. Moreover, we have found histone and DNA modifications typically associated with repressive chromatin, particularly H3K27me3, H3K4me1, and 5‐mC, in undifferentiated ES cells, and permissive marks, specifically H3K4me3 and H3K27Ac, in stem cells that have been subjected to differentiation [62]. Remarkably, OCT4 interactome analysis in ES cells has revealed that this TF physically interacts with proteins associated with gene repression, such as Sin3a, Chd4, and Mbd3 [67,68].…”