The X-linked mental retardation gene PHF8 is a histone demethylase involved in neuronal differentiation

Abstract

Recent studies have identified mutations in PHF8, an X-linked gene encoding a JmjC domain-containing protein, as a causal factor for X-linked mental retardation (XLMR) and cleft lip/cleft palate. However, the underlying mechanism is unknown. Here we show that PHF8 is a histone demethylase and coactivator for retinoic acid receptor (RAR). Although activities for both H3K4me3/2/1 and H3K9me2/1 demethylation were detected in cellularbased assays, recombinant PHF8 exhibited only H3K9me2/1 demethylase activity in vitro, suggesting that PHF8 is an H3K9me2/1 demethylase whose specificity may be modulated in vivo. Importantly, a mutant PHF8 (phenylalanine at position 279 to serine) identified in the XLMR patients is defective in enzymatic activity, indicating that the loss of histone demethylase activity is causally linked with the onset of disease. In addition, we show that PHF8 binds specifically to H3K4me3/2 peptides via an N-terminal PHD finger domain. Consistent with a role for PHF8 in neuronal differentiation, knockdown of PHF8 in mouse embryonic carcinoma P19 cells impairs RA-induced neuronal differentiation, whereas overexpression of the wild-type but not the F279S mutant PHF8 drives P19 cells toward neuronal differentiation. Furthermore, we show that PHF8 interacts with RARα and functions as a coactivator for RARα. Taken together, our results suggest that histone methylation modulated by PHF8 plays a critical role in neuronal differentiation.

The reduced and altered activities of PAX5 are linked to the protein–protein interaction motif (coiled-coil domain) of the PAX5–PML fusion protein in t(9;15)-associated acute lymphocytic leukemia

“…The next question we want to address is whether or not wild-type PML, could be recruited into the chromatin region occupied by PAX5-PML fusion protein. Toward this end, the potential interaction between PAX5-PML and PML in the context of chromatin was studied using the lac operator/lac repressor tethering system (Qiu et al, 2007(Qiu et al, , 2010a. The coexpression of GFP-LacR-PAX5-PML with ChFP-PML in A03_1 cells showed that part of the ChFP-PML colocalized with GFP-LacR-PAX5-PML on the lac operator array, although the plenty of ChFP-signal still remained in the PML nuclear body (Koken et al, 1994) (Figure 4a, first row), suggested that wild-type PML could form PML/PAX5-PML/DNA complex in the context of chromatin.…”

“…Cells with transient expression of GFP-LacR-tagged plus ChFPtagged constructs (in A03_1 cell) and YFP-PAX5-PML, YFP-PAX5-PML(DCC), YFP-PAX5, YFP-5 0 -PAX5 or YFP-3 0 -PML (in HeLa and 293T cell) were fixed and deconvolution microscopy was performed as described previously (Qiu et al, 2006(Qiu et al, , 2007(Qiu et al, , 2010a.…”

Features of the PHF8/KIAA1718 histone demethylase

“…The biological significance of PHF8 demethylation was studied by Qiu et al, who showed that loss of PHF8 demethylation, for example in XLMR, affects retinoic acid (RA)-induced neuronal differentiation [11]. Interestingly, ChIP data revealed that PHF8 is recruited to target genes of the RA receptor (RAR), where it functions as an RAR coactivator [11].…”

“…Interestingly, ChIP data revealed that PHF8 is recruited to target genes of the RA receptor (RAR), where it functions as an RAR coactivator [11]. RARα-driven transcription was reduced in cells expressing a catalytic mutant (H247A) of PHF8 compared to cells expressing WT PHF8.…”

Expression profiles of histone lysine demethylases during cardiomyocyte differentiation of mouse embryonic stem cells

“…Phf8 preferentially acts on H3K9me2 and H3K9me1 and associates with transcriptional activation and retinoic acid signaling pathways in neuron differentiation [37] . Jhdm1d controls brain development by activating follistatin gene transcription [38] .…”