BET bromodomain inhibition has contributed new insights into gene regulation and emerged as a promising therapeutic strategy in cancer. Structural analogy of early methyl-triazolo BET inhibitors has prompted a need for structurally dissimilar ligands as probes of bromodomain function. Using fluorous-tagged multicomponent reactions, we developed a focused chemical library of bromodomain inhibitors around a 3,5-dimethylisoxazole biasing element with micromolar biochemical IC50. Iterative synthesis and biochemical assessment allowed optimization of novel BET bromodomain inhibitors based on an imidazo[1,2-a]pyrazine scaffold. Lead compound 32 (UMB-32) binds BRD4 with a Kd of 550 nM and 724 nM cellular potency in BRD4-dependent lines. Additionally, compound 32 shows potency against TAF1, a bromodomain-containing transcription factor previously unapproached by discovery chemistry. Compound 32 was cocrystallized with BRD4, yielding a 1.56 Å resolution crystal structure. This research showcases new applications of fluorous and multicomponent chemical synthesis for the development of novel epigenetic inhibitors.

Accumulating evidence has demonstrated that microRNAs (miRNAs) play critical roles in cancer initiation and development by functioning either as oncogenes or as tumor suppressors. The role of microRNA-449a (miR-449a) in endometrial cancer remains unclear. We examined the levels of miR-449a and miR-449b in benign endometrium, type I and type II endometrial cancer tissues by quantitative real-time polymerase chain reaction. To further investigate the roles of miR-449a in regulating the behavior of endometrial cancer cells, we overexpressed miR-449a in the endometrial cancer cell line HEC-1B, which had low endogenous miR-449a expression. We analyzed the effects of miR-449a overexpression on CDC25 expression, proliferation, invasion and apoptosis of HEC-1B cells. We found that miR-449a and miR-449b levels were markedly reduced in type II endometrial cancer tissues but not in type I endometrial cancer tissues compared with normal endometrium. Overexpression of miR-449a significantly inhibited the proliferation, invasion and clonogenic survival of HEC-1B cells. MiR-449a overexpression also induced apoptosis in HEC-1B cells. In addition, real-time RT-PCR and western blot analysis showed that CDC25A expression was suppressed by miR-449a overexpression. Our results suggest that miR-449a may act as a tumor suppressor by targeting CDC25A in endometrial cancer.

Methyl-CpG binding protein 2 (MeCP2) is a chromatin regulator highly expressed in mature neurons. Mutations of MECP2 gene cause Ͼ90% cases of Rett syndrome, a neurodevelopmental disorder featured by striking psychomotor dysfunction. In Mecp2-null mice, the motor deficits are associated with reduction of dopamine content in the striatum, the input nucleus of basal ganglia mostly composed of GABAergic neurons. Here we investigated the causal role of MeCP2 in modulation of striatal dopamine content and psychomotor function. We found that mice with selective removal of MeCP2 in forebrain GABAergic neurons, predominantly in the striatum, phenocopied Mecp2-null mice in dopamine deregulation and motor dysfunction. Selective expression of MeCP2 in the striatum preserved dopamine content and psychomotor function in both males and females. Notably, the dopamine deregulation was primarily confined to the rostral striatum, and focal deletion or reactivation of MeCP2 expression in the rostral striatum through adeno-associated virus effectively disrupted or restored dopamine content and locomotor activity, respectively. Together, these findings demonstrate that striatal MeCP2 maintains local dopamine content in a non-cell autonomous manner in the rostral striatum and that is critical for psychomotor control. Key words: dopamine; methyl-CpG binding protein 2; motor control; Rett syndrome; striatum IntroductionRett Syndrome (RTT) is a neurodevelopmental disorder primarily affecting females. Numerous RTT patients develop stereotypical hand wringing with ambulatory difficulties; these motor symptoms usually exacerbate with age and resemble Parkinson's symptoms later in life (Chahrour and Zoghbi, 2007; Temudo et al., 2008). More than 90% of RTT cases are caused by mutations in the X-linked gene encoding methyl-CpG binding protein 2 (MeCP2; Amir et al., 1999). The MeCP2 protein is highly expressed in mature neurons and is involved in regulating target gene transcription (Chahrour and Zoghbi, 2007;Guy et al., 2011). Loss of MeCP2 in mice mimics many RTT-like symptoms including late onset hypoactivity and deficits in motor coordination and motor skill learning (Chen et al., 2001;Guy et al., 2001;Shahbazian et al., 2002; Goffin et al., 2012;Kao et al., 2015). These motor phenotypes have been previously linked to reduced dopamine synthesis in the midbrain dopaminergic neurons (Samaco et al., 2009;Gantz et al., 2011; Panayotis et al., 2011). However, MeCP2 deficiency in aminergic neurons does not show motor learning impairments (Samaco et al., 2009), and selective expression of MeCP2 in catecholamine neurons of Mecp2-deficient mice partially ameliorate the RTT-like motor deficits , raising the possibility that MeCP2 in noncatecholamine neurons also plays a role in psychomotor control.We previously found that Mecp2-null mice show psychomotor deficits associated with aberrant molecular and cellular phenotypes in the striatum (Kao et al., 2015). The striatum is the input nucleus of the basal ganglia that resides in the forebrain and contr...

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