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Abstract: The “Operon paper” by F. Jacob and J. Monod started 50 years of research into understanding how the expression of genes is regulated on a molecular level. Ten years ago, microRNAs (miRNAs) emerged as major regulators of eukaryotic gene expression. Here, I will review the basic principles of gene regulation by miRNAs and how these principles can be linked to insights from the Operon paper. A lot of what is understood about miRNAs required a combination of computational and experimental methods. I will discuss some examples that illustrate the power of this approach. [Copyright &y& Elsevier]

Abstract: In rodents, the transcription factors early growth response 2 (EGR2) and sterol regulatory element binding protein 1a (SREBP1a) regulate transcription of the stearoyl-CoA desaturase 2 (SCD2) gene during peripheral nerve myelination, which may be important for synthesis of the lipid component of myelin. Most non-rodent genomes do not contain the SCD2 gene, but rather express SCD5 in brain and nervous tissues. In this paper, we asked whether bovine SCD5 is regulated in a similar manner to rodent SCD2. Expression of EGR2 did not result in an increase in endogenous SCD5 mRNA expression in JEG3 cells, but did result in activation of truncated bovine SCD5 promoter luciferase reporter constructs. Similar results were obtained with expression of the active form of SREBP1a; however, unlike rodent SCD2, there was no synergistic activation of the bovine SCD5 promoter reporters when EGR2 and SREBP1a were co-expressed. Mutation of the putative EGR2 binding site in the SCD5 promoter abolished activation by SREBP1a, suggesting that EGR2 and SREBP1a bind to the same site in the SCD5 promoter. Finally, we have identified a region of the bovine SCD5 promoter between 505 and 305 base pairs upstream of the transcriptional start site that appears to be important for maintaining basal levels of transcription of this gene. While it appears that there are some differences between the regulation of rodent SCD2 and bovine SCD5, the promoters of both genes can be activated by EGR2 and SREBP1a. This is the first report of potential regulators of SCD5 transcription. [Copyright &y& Elsevier]

Abstract: The nuclear membrane has an important role for the dynamic regulation of the genome, besides the well-established cytoskeletal function. The nuclear lamina is emerging as an important player in the organization of the position and functional state of interphase chromosomes. Epigenetic modifications such as DNA methylation and histone modifications are required for genome reprogramming during development, tissue-specific gene expression and global gene silencing. The Methyl-CpG binding protein MeCP2 binds methyl-CpG dinucleotides in the mammalian genome and functions as a transcriptional repressor in vivo by interacting with Sin3A, thereby recruiting histone deacetylases (HDAC). MeCP2 also mediates the formation of higher-order chromatin structures contributing to determine the architectural organization of the nucleus. In this paper, we show that MeCP2 interacts in vitro and in vivo with the inner nuclear membrane protein LBR and that the unstructured aminoacidic sequence linking the MBD and TRD domains of MeCP2 is responsible for this association. The formation of an LBR–MeCP2 protein complex might help providing a molecular explanation to the distribution of part of the heterochromatin at the nuclear periphery linked to inner membrane. [Copyright &y& Elsevier]