p53-Targeted LSD1 Functions in Repression of Chromatin Structure and Transcription In Vivo

Abstract

Despite years of study focused on the tumor suppressor p53, little is understood about its functions in normal, differentiated cells. We found that p53 directly interacts with lysine-specific demethylase 1 (LSD1) to alter chromatin structure and confer developmental repression of the tumor marker alpha-fetoprotein (AFP). Chromatin immunoprecipitation (ChIP) and sequential ChIP of developmentally staged liver showed that p53 and LSD1 cooccupy a p53 response element, concomitant with dimethylated histone H3 lysine 4 (H3K4me2) demethylation and postnatal repression of AFP transcription. In p53-null mice, LSD1 binding is depleted, H3K4me2 is increased, and H3K9me2 remains unchanged compared to those of the wild type, underscoring the specificity of p53-LSD1 complexes in demethylation of H3K4me2. We performed partial hepatectomy of wild-type mouse liver and induced a regenerative response, which led to a loss of p53, increased H3K4me2, and decreased LSD1 interaction at AFP chromatin, in parallel with reactivation of AFP expression. In contrast, nuclear translocation of p53 in mouse embryonic fibroblasts led to p53 interaction with p21/CIP1 chromatin, without recruitment of LSD1, and to activation of p21/CIP1. These findings reveal that LSD1 is targeted to chromatin by p53, likely in a gene-specific manner, and define a molecular mechanism by which p53 mediates transcription repression in vivo during differentiation.Numerous analyses of p53 functions, in response to cellular stress, underscore its important, pleiotropic roles in arrest of the cell cycle and promotion of apoptosis (5,24,33). Less understood are mechanisms of p53-mediated regulation during differentiation and in maintenance of cellular homeostasis. Previous work from our laboratory established p53 as a major repressor of AFP transcription during hepatic development (60). Developmental repression of AFP, an onco-fetal tumor marker gene, is delayed more than 2 months after birth in p53-null mice, compared to cessation within 2 to 3 weeks in wild-type (WT) mice (45). Transactivating p73 (TA-p73), but not TA-p63, partially compensates for an absence of p53 in p53-null mice, characterized by elevated methylation of histone H3 lysine 4 (H3K4) at the p53/p73 response element of alpha-fetoprotein (AFP) chromatin (12). Therefore, we hypothesized that an H3K4 demethylase is recruited by p53 during hepatic differentiation and that combinatorial alterations in chromatin structure during development dictate the developmental timing of transcription regulation.Enzymatic removal of methyl groups from lysine residues of histone N-terminal tails correlates with either repression or activation of transcription, as determined by the specific histone substrate, amino acid position, and level of methylation. Loss of methylated H3K4 (H3K4me) is generally associated with repression or cessation of active transcription (7,14,55).The first enzyme with the capacity to remove methyl groups from histone lysine residues was identified as BHC110 or histone lysine-specific demethylas...

Involvement of Histone Demethylase LSD1 in Blimp-1-Mediated Gene Repression during Plasma Cell Differentiation

“…8H), indicating that LSD1 depletion is not sufficient to alter H3K9me2 modification mediated by G9a. This result is accordant with a recent report that LSD1 depletion does not change the H3K9me2 level in a p53-responsive element bound by p53 and LSD1 (47). Here, we found that H3K4me1 levels were neither sensitive to LSD1 depletion (Fig.…”

Loss of lysine-specific demethylase 1 nonautonomously causes stem cell tumors in the Drosophila ovary

“…The histone demethylase Lsd1 emerged as a likely candidate based on its role in various developmental processes. In humans, loss of Lsd1 has been linked to several highrisk cancers (15)(16)(17) and Lsd1 has recently been shown to regulate the transcription of TGF β1, a Dpp homolog, negatively (18). Previous work has shown that Drosophila Lsd1 mutants display male and female sterile phenotypes and defects in heterochromatin formation (19,20).…”

“…Recent studies show that mammalian Lsd1 directly targets TGF-β1 for transcriptional repression (18) and has cell-autonomous roles in cancer (15)(16)(17)(18). Given the possible links between cancer and stem cells (42) and the observation that Lsd1 has a conserved role in regulating intercellular signaling molecules, it will be important to determine whether Lsd1 and other chromatin factors have additional nonautonomous functions that contribute to stem cell maintenance, tumorigenesis, and metastasis.…”

Rap2b, a novel p53 target, regulates p53-mediated pro-survival function

“…24,50 p53 can directly repress gene transcription by recruiting co-repressor, such as Sin3a and LSD1, or interfere with the enhancer activity. 25,[51][52][53] Or it can indirectly repress its targets by inducing other transcriptional factors, for example, E2F7 or noncoding RNAs, such as lincRNAs or miRNAs, which, in turn, repress its targets. 29,30,54 Therefore, p53 may use many different mechanisms to conduct transcriptional repression in different cell types to fulfill its cell type-specific functions.…”