The C. elegans SET-2/SET1 histone H3 Lys4 (H3K4) methyltransferase preserves genome stability in the germline.

Maintaining the integrity of genetic information across generations is essential for both cell survival and reproduction, and requires the timely repair of DNA damage. Histone-modifying enzymes play a central role in the DNA repair process through the deposition and removal of post-translational modifications on the histone tails. Specific histone modification act in the DNA repair process through the recruitment of proteins and complexes with specific enzymatic activities, or by altering the chromatin state at the site of DNA lesions. The conserved SET1/MLL family of histone methyltransferases (HMT) catalyzes methylation of histone H3 on Lysine 4 (H3K4), a histone modification universally associated with actively transcribed genes. Studies have focused on the role of SET1/MLL proteins in epigenetic regulation of gene expression. Much less is known on their role in the DNA repair process in a developmental context. Here we show that SET-2, the Caenorhabditis elegans orthologue of SET1, is required to preserve germline genome integrity over subsequent generations. Animals lacking the SET-2 catalytic subunit show a transgenerational increase in sensitivity to DNA damage-inducing agents that is accompanied by a defect in double-strand break (DSB) repair and chromosome fragmentation. These defects are not due to a failure to activate the DNA damage response (DDR) that allows detection, signaling and repair of DNA lesions, because cell cycle arrest and apoptosis, key components of this pathway, are efficiently induced in set-2 mutant animal. Rather, our results suggest that SET-2 plays a role in the transgenerational maintenance of genome stability by acting in DNA repair downstream of DDR signaling.

New pyridobenzodiazepine derivatives as potential antipsychotics: synthesis and neurochemical study.

The discovery of a new, safe, atypical antipsychotic remains an important challenge. To achieve this goal, a series of N-methylpiperazinopyrido[2,3-b] [1,4]- and -[1,5]- and -pyrido[4,3-b][1,4]- and -[1,5]- benzodiazepines were synthesized. The dopaminergic (D1, D2), serotonergic (5-HT2), and cholinergic (M) affinities, frequently remarked in the action mechanisms of antipsychotic drugs, were determined using their respective in vitro receptor binding assays. All affinities were reduced for each compound. Optimal substituents were found to be in the 2- or 8-position for the retention of affinities, while substitution at the 5-position by acyl or alkyl groups dramatically diminished binding affinities. Pyridobenzodiazepine derivatives, such as clozapine, were found to be inactive or only weakly effective against apomorphine-mediated stereotypes in rats. In an original and complex behavioral model developed in dogs and successfully used to differentiate distinct classes of psychotropic drugs and to discriminate between typical and atypical neuroleptic drugs, 8-chloro-6-(4-methyl-1-piperazinyl)-11H-pyrido[2,3-b] [1,4]benzodiazepine (9), 8-methyl-6-(4-methyl-1-piperazinyl)-11H-pyrido [2,3-b][1,4]benzodiazepine (12), and 5-(4-methyl-1-piperazinyl)-11H-pyrido[2,3-b][1,5]benzodiazepine (16) showed most of the behavioral characteristics previously described for neuroleptics. Their neurochemical profiles, particularly their 5-HT2/D2 pKi ratios, were compatible with an atypical antipsychotic effect. These compounds were selected for further investigation. The proposed modulations could lead to new possibilities for the pharmacochemistry of diarylazepines.

Pyridobenzoxazepine and pyridobenzothiazepine derivatives as potential central nervous system agents: synthesis and neurochemical study.

In order to characterize the pharmacological profile of the different chemical classes of pyridobenzazepine derivatives, a series of N-methylpiperazinopyrido[1,4]- and -[1,5]- benzoxa- and benzothiazepine derivatives were prepared. The affinities for D2, D1, 5-HT2, and cholinergic (M) receptors were measured. In comparison to dibenzazepine reference compounds, a strong decrease of the affinities was observed, less pronounced, however, for the substituted analogues. Oxazepine and thiazepine analogues like clozapine (except 8-chloro-6-(4-methylpiperazin-1-yl)-pyrido[2,3-b][1,4]benzoxazepin e (9) and 8-chloro-6-(4-methylpiperazin-1-yl)pyrido[2,3-b][1,4]- benzothiazepine (11)) were found to be inactive against apomorphine stereotypies. In the open-field test in rats, different molecules showed a high disinhibitory activity as observed with anxiolytic drugs. Moreover, 8-chloro-5-(4-methylpiperazin-1-yl)pyrido[2,3-b][1,5]benzoxazepine (14) presented a clozapine-like profile that was confirmed in the behavioral model in dogs and showed most of the behavioral characteristics described for antipsychotic drugs. Its neurochemical profile, in particular the 5-HT2/D2 ratio, was also compatible with atypical antipsychotic activity.