Biomedical subjects

Juan Jimenez

Publications and source records attributed to Juan Jimenez.

4 recordsLinked to original sources

PubMed2006

Adaptive evolution by mutations in the FLO11 gene.

In nature, Saccharomyces yeasts manifest a number of adaptive responses to overcome adverse environments such as filamentation, invasive growth, flocculation and adherence to solid surfaces. Certain Saccharomyces wild yeasts, namely "flor yeasts," have also acquired the ability to form a buoyant biofilm at the broth surface. Here we report that mutations in a single gene, identified as FLO11, separate these "floating" yeasts from their nonfloating relatives. We have determined that the capability to form a self-supporting biofilm at the liquid surface is largely dependent on two changes in the FLO11 gene. First, we identified a 111-nt deletion within a repression region of the FLO11 promoter that significantly increases FLO11 gene expression. Secondly, we found rearrangements within the central tandem repeat domain of the coding region that yield a more hydrophobic Flo11p variant. Together, these mutations result in dramatic increase in cell surface hydrophobicity, which in turn confers these yeasts the ability to float by surface tension, an adaptive mechanism to gain direct access to oxygen within oxygen-poor liquid environments.

Alleles↗

PubMed2005

Etd1p is a novel protein that links the SIN cascade with cytokinesis.

In animal cells, cytokinesis occurs by constriction of an actomyosin ring. In fission yeast cells, ring constriction is triggered by the septum initiation network (SIN), an SPB-associated GTPase-regulated kinase cascade that coordinates exit from mitosis with cytokinesis. We have identified a novel protein, Etd1p, required to trigger actomyosin ring constriction in fission yeasts. This protein is localised at the cell tips during interphase. In mitosis, it relocates to the medial cortex region and, coincident with cytokinesis, it assembles into the actomyosin ring by association to Cdc15p. Relocation of Etd1p from the plasma membrane to the medial ring is triggered by SIN signalling and, reciprocally, relocation of the Sid2p-Mob1p kinase complex from the SPB to the division site, a late step in the execution of the SIN, requires Etd1p. These results suggest that Etd1p coordinates the mitotic activation of SIN with the initiation of actomyosin ring constriction. Etd1p peaks during cytokinesis and is degraded by the ubiquitin-dependent 26S-proteasome pathway at the end of septation, providing a mechanism to couple inactivation of SIN to completion of cytokinesis.

Actomyosin↗

PubMed2002

Genome-wide search of Schizosaccharomyces pombe genes causing overexpression-mediated cell cycle defects.

Genetic studies in yeasts enable an in vivo analysis of gene functions required for the cell division cycle (cdc genes) in eukaryotes. In order to characterize new functions involved in cell cycle regulation, we searched for genes causing cell division defects by overexpression in the fission yeast Schizosaccharomyces pombe. By using this dominant genetic strategy, 26 independent clones were isolated from a Sz. pombe cDNA library. The cloned cDNAs were partially sequenced and identified by computer analysis. The 26 clones isolated corresponded to 21 different genes. Among them, six were genes previously characterized in Sz. pombe, 11 were homologues to genes identified and characterized in other organisms, and four represented genes with unknown functions. In addition to known cell cycle regulators encoding inhibitory protein kinases (wee1, pka1) and DNA checkpoint proteins (Pcna, rad24), we have identified genes that are involved in a number of cellular processes. This includes protein synthesis (ribosomal proteins L7, L10, L29, L41, S6, S11, S17 and the PolyA-Binding Protein PABP), protein degradation (UBI3), nucleolar rRNA expression (fib, imp1, dbp2), cell cytoskeleton (act1) and glycolysis (pfk1). The interference caused in the cell cycle by overexpression of these genes may elucidate novel mechanisms coupling different cellular processes with the control of the cell division. The effect caused by some of them is described in more detail.

Actins↗

PubMedDate not supplied

Comparison of the results of percutaneous transluminal angioplasty and stenting with medical treatment for claudicants who have superficial femoral artery occlusive disease.

The outcomes of medical management of peripheral vascular disease localized to the superficial femoral artery (SFA) were compared with those obtained by percutaneous transluminal angioplasty (PTA) with or without stenting in a review of selected studies. The natural history of localized SFA disease is favorable, with major amputation rates less than 10% and revascularization in only 18% of patients over a 10-year interval. Conservative treatment of claudicants shows increases (150%) in walking distance if the ankle brachial index (ABI) is over 0.6 and patients stop smoking. Analysis of 10 trials (882 patients) of PTA with or without stenting found that the overall primary patency rates at 12 months were 71.1% for PTA plus stenting and 58.3% for PTA alone. Technical success with PTA with or without stenting is over 90%, and early results at 6 months are superior to those with exercise. In three randomized controlled trials, however, the difference between PTA and medical treatment at 2 years, whether measured by walking distance or ABI, was not significant, nor was the quality of life. For long-term improvement in walking distance (> 1 year) in the claudicant, intervention is not superior to medical treatment and a monitored exercise program. Consideration should be given to including a nonintervention control group and 2-year outcomes in the evaluation of new SFA stents.

Angioplasty, Balloon↗