RESUMO
Nuclear receptors (NRs) are ligand-activated transcription factors that play an important role in metabolism, homeostasis, differentiation and development regulation. NRs are also involved in pathogenesis of various diseases. For most of NRs natural ligands are known. Ligand-activated NRs bind specific nucleotide sequences in target genes and induce their expression. DAX1 protein is an unusual member of NR superfamily that does not have ligand and lacks typical DNA-binding domain. It was established 20 years ago that DAX1 plays a critical role in regulation of adrenal and gonadal development and in biosynthesis of steroid hormones, however the molecular mechanisms of its action remained not fully understood. Further studies have shown that this piotein can interact with many members of NR superfamily and with different co-repressors and co-activators of transcription. Its functions are not restricted to regulation of adrenal and gonadal development and steroidogenesis. Recent studies have elucidated the role of DAX1 in pathogenesis of X-linked adrenal congenital hypoplasia and dose-sensitive sex reversal. It was found also that DAX1 is an important component of transcription factors network that maintains the pluripotency of mouse embryonic stem Cells. Here we review the current knowledge on properties, functions and mechanisms of DAX1 action. The role of DAX1 in pathogenesis of inherited diseases is discussed. The specificity of DAX1 interaction with various protein.partners is characterized. The examples of co-repressor and coactivator action of DAX1 on transcription are presented. The potential association of DAX1 with oncoendocrine pathologies and its role in self-renewal of mouse embryonic stem cells are described.
Assuntos
Hiperplasia Suprarrenal Congênita/genética , Receptor Nuclear Órfão DAX-1/genética , Células-Tronco Embrionárias/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/genética , Receptores Citoplasmáticos e Nucleares/genética , Hiperplasia Suprarrenal Congênita/patologia , Insuficiência Adrenal , Motivos de Aminoácidos , Animais , Receptor Nuclear Órfão DAX-1/metabolismo , Proteínas de Ligação a DNA/genética , Doenças Genéticas Ligadas ao Cromossomo X/patologia , Hormônios Esteroides Gonadais/genética , Humanos , Hipoadrenocorticismo Familiar , Ligantes , Camundongos , Receptores Citoplasmáticos e Nucleares/metabolismo , Fatores de Transcrição/genéticaRESUMO
In the genomes of humans and other mammals a large number of closely spaced pairs of genes that are transcribed in opposite directions were revealed. Their transcription is directed by so-called bidirectional promoters. This review is devoted to the characteristics of bidirectional promoters and features of their structure. The composition of "core" promoter elements in conventional unidirectional and bidirectional promoters is compared. Data on binding sites of transcription factors that are primarily specific for bidirectional promoters are discussed. The examples of promoters that share protein-coding genes transcribed by RNA polymerase II and the non-coding RNA genes transcribed by RNA polymerase III are described. Data obtained from global transcriptome analysis about the existence of short noncoding antisense RNA associated with the promoters in the context of the hypothesis of bidirectional transcription initiation as an inherent property of eukaryotic promoters are discussed.
Assuntos
Genoma/genética , Mamíferos/genética , Regiões Promotoras Genéticas/genética , Transcrição Gênica/genética , Animais , Humanos , RNA Polimerase II/metabolismoRESUMO
In human and other mammalian genomes a number of closely linked gene pairs transcribed in opposite directions are found. According to bioinformatic analysis up to 10% of human genes are arranged in this way. In present work the fragment of human genome was cloned that separates genes localized at 2p13.1 and oriented "head-to-head", coding for hypothetical proteins with unknown functions--CCDC (Coiled Coil Domain Containing) 142 and TTC (TetraTricopeptide repeat Containing) 31. Intergenic CCDC142-TTC31 region overlaps with CpG-island and contains a number of potential binding sites for transcription factors. This fragment functions as bidirectional promoter in the system ofluciferase reporter gene expression upon transfection of human embryonic kidney (HEK293) cells. The vectors containing genes of two fluorescent proteins--green (EGFP) and red (DsRed2) in opposite orientations separated by the fragment of CCDC142-TTC31 intergenic region were constructed. In HEK293 cells transfected with these vectors simultaneous expression of two fluorescent proteins is observed. Truncated versions of intergenic region were obtained and their promoter activity measured. Minimal promoter fragment contains elements Inr, BRE, DPE characteristic for TATA-less promoters. Thus, from the human genome the novel bidirectional promoter was cloned that can be used for simultaneous constitutive expression of two genes in human cells.