Produit génique | EPFL Graph Search

Un produit génique est une biomolécule résultant de l'expression d'un gène. Il peut s'agir d'un fragment, soit d'ARN, soit de protéine. La mesure de la quantité de produits géniques est parfois utilisée pour évaluer l'activité d'un gène, comme dans le cas des oncogènes, dont la surexpression peut entraîner des cancers. Notes et références Catégorie:Expression génétique

Surface modification of PES virus filtration membrane

Claire Roulin

Virus filtration by size exclusion is a robust means of eliminating viruses in blood or pharma products. Porous polymer membranes with a narrow size distribution are used to allow passage of the protein product but retain viruses. The chosen polymer must resist process-induced physical and chemical wear and is therefore generally inert and hydrophobic material. When filtrating potentially heterogeneous products such as IgG from pooled blood samples, protein adsorption on the polymer surface causes high fouling. This eventually blocks the filter and reduces total filtration volume. A solution to this adsorption problem is to graft a hydrophilic gel-like polymer layer on the membrane inner surface to reduce protein adsorption. The surface properties are thus changed while retaining the stability of the bulk polymer. The grafting was initiated with an electron beam, which creates free radicals by unspecific scission of the polymer backbone through electron irradiation. Two acrylate monomers were used for polymerization, a monofunctional monomer and a bifunctional one, used as a crosslinker to form the gel structure. Two different grafting method were tested. The first grafting method is simultaneous grafting, where the membrane is impregnated with the monomer solution then irradiated. Initiation and polymerization thus occur almost simultaneously. The grafted membrane properties were assessed using flow measurements, protein adsorption tests, FTIR absorbance measurements, virus retention tests and filter integrity tests. Comparing the various grafting approaches, it can be seen that simultaneous grafting lowers considerably protein adsorption, to the price of a highly reduced buffer flow. These filters therefore run slowly but can process more volume before fouling. The sequential grafting method using peroxides as initiators did not show significant filtration improvements compared to the reference membrane when the solution with monomer and crosslinker was used. However, when only monofunctional monomer was used for peroxidation grafting, the protein filtration capacity was increased with limited buffer flow loss. Generally, the sequential method is interesting for graft polymerization of porous membranes because it allows higher degree of grafting and the versatile grafting parameters involved give many development options depending on the application

2010

Isolation and Characterisation of Regulators of the Septation Initiation Network Regulators in Fission Yeast

Anupama Goyal

The septation initiation network (SIN) in Schizosaccharomyces pombe regulates cytokinesis. Cdc7p encodes the first kinase in the core SIN pathway. In this study, I performed a genetic screen to identify novel regulators of the SIN pathway by isolating spontaneous revertants of cdc7-24 that displayed a cold-sensitive phenotype. The screen yielded a cold-sensitive allele of ppa2, the major PP2A catalytic subunit, and a mutant in ypa2, one of the two S. pombe PTPA orthologues. I characterised both the PTPA genes in the fission yeast, namely, ypa1 and ypa2. It was determined that both ypa1 and ypa2 are essential for survival at low temperatures. The double null mutant was found to be inviable at all temperatures, indicating that the two gene products have at least one essential overlapping function. It was also established that Ypa2p is the major form of PTPA in S. pombe. Characterisation of the phenotype of the ppa2 and ypa2 mutants suggest that the PP2A complex is involved in establishment of cell morphogenesis, determining site of division plane, the G2/M transition and separation of the divided cells. Genetic interactions of the ypa2 and ppa2 mutants with the SIN mutants suggest that reduction in PP2A activity rescues SIN mutants. It was also determined that ypa2 and ppa2 play a role in regulating asymmetric localisation of Cdc7p during mitosis and association of Sid2p with the contractile actomyosin ring.

EPFL2012

Characterisation of ypa1 and ypa2, the Schizosaccharomyces pombe orthologues of the peptidyl proyl isomerases that activate PP2A, reveals a role for Ypa2p in the regulation of cytokinesis

Anupama Goyal, Viesturs Simanis

The Schizosaccharomyces pombe septation initiation network regulates cytokinesis. Cdc7p is the first kinase in the core septation initiation network; we have screened genetically for SIN regulators by isolating cold-sensitive suppressors of cdc7-24. Our screen yielded a mutant in SPAC1782.05, one of the two fission yeast orthologues of mammalian phosphotyrosyl phosphatase activator. We have characterised this gene and its orthologue SPAC4F10.04, which we have named ypa2 and ypa1, respectively. We find that Ypa2p is the major form of Protein Phosphatase Type 2A activator in S. pombe. A double ypa1-Δ ypa2-Δ null mutant is inviable, indicating that the two gene products have at least one essential overlapping function. Individually, the ypa1 and ypa2 genes are essential for survival only at low temperatures. The ypa2-Δ mutant divides at a reduced cell size, and displays aberrant cell morphology and cytokinesis. Genetic analysis implicates Ypa2p as an inhibitor of the septation initiation network. We also isolated a cold-sensitive allele of ppa2, the major Protein Phosphatase Type 2A catalytic subunit, implicating this enzyme as a regulator of the septation initiation network.

2012

Surface modification of PES virus filtration membrane

Claire Roulin

2010