Biomedical subjects

Mathieu Gabut

Publications and source records attributed to Mathieu Gabut.

5 recordsLinked to original sources

PubMed2006

SR proteins as potential targets for therapy.

Serine- and arginine-rich (SR) proteins constitute a highly conserved family of pre-mRNA splicing factors that play key roles in the regulation of splice site selection, and thereby in the control of alternative splicing processes. In addition to conserved sequences at the splice junctions, splice site selection also depends upon different sets of auxiliary cis regulatory elements known as exonic and intronic splicing enhancers (ESEs and ISEs) or exonic and intronic silencers (ESSs and ISSs). Specific binding of SR proteins to their cognate splicing enhancers as well as binding of splicing repressor to silencer sequences serve to enhance or inhibit recognition of weak splice sites by the splicing machinery. Given that the vast majority of human genes contain introns and that most pre-mRNAs containing multiple exons undergo alternative splicing, mutations disrupting or creating such auxiliary elements can result in aberrant splicing events at the origin of various human diseases. In the past few years, numerous studies have reported several approaches allowing correction of such aberrant splicing events by targeting either the mutated sequences or the splicing regulators whose binding is affected by the mutation. The aim of the present review is to highlight the different means by which it is possible to modulate the activity of SR splicing factors and to bring out those holding the greatest promises for the development of therapeutic treatments.

Aclarubicin↗

PubMed2005

Selective modification of alternative splicing by indole derivatives that target serine-arginine-rich protein splicing factors.

The prevalence of alternative splicing as a target for alterations leading to human genetic disorders makes it highly relevant for therapy. Here we have used in vitro splicing reactions with different splicing reporter constructs to screen 4,000 chemical compounds for their ability to selectively inhibit spliceosome assembly and splicing. We discovered indole derivatives as potent inhibitors of the splicing reaction. Importantly, compounds of this family specifically inhibit exonic splicing enhancer (ESE)-dependent splicing, because they interact directly and selectively with members of the serine-arginine-rich protein family. Treatment of cells expressing reporter constructs with ESE sequences demonstrated that selected indole derivatives mediate inhibition of ESE usage in vivo and prevent early splicing events required for HIV replication. This discovery opens the exciting possibility of a causal pharmacological treatment of aberrant splicing in human genetic disorders and development of new antiviral therapeutic approaches.

Alternative Splicing↗

PubMed2005

The SR protein SC35 is responsible for aberrant splicing of the E1alpha pyruvate dehydrogenase mRNA in a case of mental retardation with lactic acidosis.

Pyruvate dehydrogenase (PDH) complex deficiency is a major cause of lactic acidosis and Leigh's encephalomyelopathies in infancy and childhood, resulting in early death in the majority of patients. Most of the molecular defects have been localized in the coding regions of the E1alpha PDH gene. Recently, we identified a novel mutation of the E1alpha PDH gene in a patient with an encephalopathy and lactic acidosis. This mutation, located downstream of exon 7, activates a cryptic splice donor and leads to the retention of intronic sequences. Here, we demonstrate that the mutation results in an increased binding of the SR protein SC35. Consistently, ectopic overexpression of this splicing factor enhanced the use of the cryptic splice site, whereas small interfering RNA-mediated reduction of the SC35 protein levels in primary fibroblasts from the patient resulted in the almost complete disappearance of the aberrantly spliced E1alpha PDH mRNA. Our findings open the exciting prospect for a novel therapy of an inherited disease by altering the level of a specific splicing factor.

Acidosis, Lactic↗

PubMed2003

Altered serine/arginine-rich protein phosphorylation and exonic enhancer-dependent splicing in Mammalian cells lacking topoisomerase I.

DNA topoisomerase I (Topo I) specifically phosphorylates arginine-serine-rich (SR proteins) splicing factors and is potentially involved in pre-mRNA-splicing regulation. Using a Topo I-deficient murine B lymphoma-derived subclone (P388-45/C) selected for its resistance to high dosage of the antitumor drug camptothecin, we show that Topo I depletion results in the hypophosphorylation of SR proteins and impairs exonic splicing enhancer (ESE)-dependent but not constitutive splicing. The Affymetrix GeneChip system analysis revealed that several alternatively spliced genes, characterized by small exons and large introns, are down-regulated in Topo I-deficient cells. Given that ectopic expression of green fluorescent protein-Topo I fusion in Topo I-deficient cells restores both wild-type phosphorylation of SR proteins and ESE-dependent splicing, we conclude that Topo I-mediated phosphorylation plays a specific role in ESE-regulated splicing.

Alternative Splicing↗

PubMed2003

Inheritance of Polycomb-dependent chromosomal interactions in Drosophila.

Maintenance of cell identity is a complex task that involves multiple layers of regulation, acting at all levels of chromatin packaging, from nucleosomes to folding of chromosomal domains in the cell nucleus. Polycomb-group (PcG) and trithorax-group (trxG) proteins maintain memory of chromatin states through binding at cis-regulatory elements named PcG response elements or cellular memory modules. Fab-7 is a well-defined cellular memory module involved in regulation of the homeotic gene Abdominal-B (Abd-B). In addition to its action in cis, we show here by three-dimensional FISH that the Fab-7 element leads to association of transgenes with each other or with the endogenous Fab-7, even when inserted in different chromosomes. These long-distance interactions enhance PcG-mediated silencing. They depend on PcG proteins, on DNA sequence homology, and on developmental progression. Once long-distance pairing is abolished by removal of the endogenous Fab-7, the derepressed chromatin state induced at the transgene locus can be transmitted through meiosis into a large fraction of the progeny, even after reintroduction of the endogenous Fab-7. Strikingly, meiotic inheritance of the derepressed state involves loss of pairing between endogenous and transgenic Fab-7. This suggests that transmission of nuclear architecture through cell division might contribute to inheritance of chromatin states in eukaryotes.

Animals↗