Synthesis and biological evaluation of 2-(5-methyl-4-phenyl-2-oxopyrrolidin-1-yl)-acetamide stereoisomers as novel positive allosteric modulators of sigma-1 receptor.

Novel positive allosteric modulators of sigma-1 receptor represented by 2-(5-methyl-4-phenyl-2-oxopyrrolidin-1-yl)-acetamide enantiomers were synthesised using an asymmetric Michael addition of 2-nitroprop-1-enylbenzene to diethyl malonate. Following the chromatographic separation of the methyl erythro- and threo-4-nitro-3R- and 3S-phenylpentanoate diastereoisomers, target compounds were obtained by their reductive cyclisation into 5-methyl-4-phenylpyrrolidin-2-one enantiomers and the attachment of the acetamide group to the heterocyclic nitrogen. Experiments with electrically stimulated rat vas deference contractions induced by the PRE-084, an agonist of sigma-1 receptor, showed that (4R,5S)- and (4R,5R)-2-(5-methyl-4-phenyl-2-oxopyrrolidin-1-yl)-acetamides with an R-configuration at the C-4 chiral centre in the 2-pyrrolidone ring were more effective positive allosteric modulators of sigma-1 receptor than were their optical antipodes.

TFIIH is an elongation factor of RNA polymerase I.

TFIIH is a multisubunit factor essential for transcription initiation and promoter escape of RNA polymerase II and for the opening of damaged DNA double strands in nucleotide excision repair (NER). In this study, we have analyzed at which step of the transcription cycle TFIIH is essential for transcription by RNA polymerase I. We demonstrate that TFIIH associates with the rDNA promoter and gene-internal sequences and leaves the rDNA promoter in a complex with RNA polymerase I after start of transcription.

A novel activity enhances promoter escape of RNA polymerase I.

We have characterized a novel transcriptional activity from HeLa cells that is required for ribosomal gene transcription by RNA polymerase I. This activity has a native molecular mass of 16 kDa and does not bind to conventional chromatographic resins. Single-round and immobilized-template experiments revealed that initiation complex formation is independent of the novel activity.

Truncated Cockayne syndrome B protein represses elongation by RNA polymerase I.

Mutations in the Cockayne syndrome B (CSB) gene result in the human form of Cockayne syndrome. CSB protein has been shown to be a component of RNA polymerase I (Pol I) transcription. In this study, we have analyzed at which step of the transcription cycle CSB influences in vitro transcription by RNA Pol I.

The transcriptional response to distinct growth factors is impaired in Werner syndrome cells.

The Werner syndrome protein (WRN) is mutated in Werner syndrome (WS) and plays a role in telomere maintenance, DNA repair and transcription. WS represents a premature aging syndrome with severe growth retardation. Here we show that WRN is critically required to mediate the stimulatory effect of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-b) and epidermal growth factor (EGF) on the activity of RNA polymerase I (Pol I).

Comparative study of CYP2B induction in the liver of rats and mice by different compounds.

Male Wistar rats and C57BL mice were treated by phenobarbital (PB), 2,4,6-triphenyldioxane-1,3 (TPD) and 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP). The CYP2B specific activities (PROD and BROD) were determined in the animal livers. PB administration significantly increased levels of PROD- and BROD-activity in the rat and mouse livers, whereas TPD induced CYP2B activities only in rat liver and TCPOBOP--only in mouse liver.