Papers by santiago torres
PLoS Pathogens, 2013
The RNAi Pathway RNA interference (RNAi) or RNA silencing is a gene regulatory system, widely con... more The RNAi Pathway RNA interference (RNAi) or RNA silencing is a gene regulatory system, widely conserved in eukaryotes, that represses gene expression through a homology-dependent mechanism. This repressive effect is mediated by small non-coding RNAs (sRNAs) of about 20-30 nucleotides, derived from double-stranded RNA (dsRNA) precursors that are recognized and processed by the RNaseIII Dicer. These sRNAs are loaded into an RNA-induced silencing complex (RISC), where the Argonaute protein plays a main role. Upon loading, the sRNAs selectively guide RISC to the target RNAs, causing their degradation or preventing their translation. In certain organisms, including fungi and parasitic protozoa, the silencing mechanism requires RNA-dependent RNA polymerases (RdRPs) to generate dsRNA from single-stranded RNA (ssRNA) or to amplify sRNA signals [1,2]. Originally described as a defense mechanism against invasive nucleic acids and viruses, RNAi and related pathways play many fundamental roles in metazoans, including regulation of mRNA accumulation and translation, chromatin silencing, programmed DNA rearrangements, and genome surveillance.
Molecular Genetics and Genomics, 2001
Mucor circinelloides responds to blue light by activating carotene biosynthesis. Wild-type strain... more Mucor circinelloides responds to blue light by activating carotene biosynthesis. Wild-type strains grown in darkness contain minimal amounts of b-carotene because of the low levels of transcription of the structural genes for carotenogenesis. When exposed to a light pulse, the level of transcription of these genes increases strongly, leading to the formation of high concentrations of b-carotene. The crgA gene is involved in the regulation of light-induced carotenoid biosynthesis. This gene, originally identi®ed as a 3¢-truncated ORF which causes carotene over-accumulation in the dark, encodes a protein with a cysteine-rich, zinc-binding, RING-®nger motif, as found in diverse groups of regulatory proteins. The expression of the crgA gene is activated by a light pulse, with a time course similar to that of the structural genes for carotenogenesis. To understand the regulatory role of the crgA gene in carotenogenesis, we have used a genetic approach based on the construction of crgA null mutants by gene replacement. Lack of the crgA function provokes the overaccumulation of carotenoids both in the dark and the light. Introduction of the wild-type crgA allele into these mutants restores the wild-type phenotype for carotenogenesis. The high levels of carotenoid accumulation shown by the null crgA mutants are correlated with an increase in the expression of carotenogenic structural genes. These results strongly indicate that crgA acts as a negative regulator of light-inducible carotenogenesis in M. circinelloides.
Genetical Research, 1980
SUMMARYThe mutations which block lycopene cyclization and those which stop substrate transfer alo... more SUMMARYThe mutations which block lycopene cyclization and those which stop substrate transfer along the carotene pathway are very closely linked inPhycomyces. Simultaneous blocking of both processes commonly results from single exposures to mutagens; and both blockings may be simultaneously removed after a second exposure. The frequencies of different kinds of mutants after treatments with the mutagensN-methyl-N′-nitro-N-nitrosoguanidine and ICR-170, their reversion patterns, and recombination analyses indicate that lycopene cyclization and substrate transfer are governed by separate segments of a single bifunctional gene.
Fungal Genetics and Biology, 1996
Nine mutants of the filamentous fungus Phycomyces blakesleeanus have been isolated on the basis o... more Nine mutants of the filamentous fungus Phycomyces blakesleeanus have been isolated on the basis of their resistance to fluoroacetate. None of the isolates uses acetate as the sole carbon source. Genetic complementation experiments revealed that all the mutants belong to the same complementation group. Biochemical analysis indicated that the acetate-induced acetyl-CoA synthetase activity is abolished in all nine mutants, thus suggesting that they are affected in the gene coding for acetyl-CoA synthetase (facA).
Fungal Genetics and Biology, 2013
Protein ubiquitylation plays a major role in the regulation of many cellular processes by alterin... more Protein ubiquitylation plays a major role in the regulation of many cellular processes by altering the stability, localization or function of target proteins. CrgA is a protein of Mucor circinelloides that shows the characteristics of ubiquitin ligases and is involved in the regulation of carotenogenesis and asexual sporulation in this fungus. CrgA, which belongs to a poorly characterized group of proteins present in almost all eukaryotes, represses carotenogenesis through the proteolysis-independent mono-and di-ubiquitylation of Mcwc-1b, a White Collar-1-like protein which, when it is non-ubiquitylated, activates carotenogenesis. Using a proteomic approach, this work shows that the regulation of M. circinelloides vegetative development by CrgA is also mediated by Mcwc-1b, although, in this case, the non-ubiquitylated Mcwc-1b form acts as a repressor. High levels of a protein that contains a classical Rossmann-fold NAD(P)H/NAD(P)(+) binding domain for NAD(P)H binding and is similar to NmrA NADP(H) sensor-like proteins occur when Mcwc-1b is inactivated by ubiquitylation. A role for this protein in the regulation of sporulation is suggested because its over-expression suppresses the sporulation defect in a crgAD mutant. NmrA-like proteins are repressors that interact with GATA transcription factors and have been shown to be related to cell differentiation in Magnaporthe oryzae and Dictyostelium discoideum. This proteomic approach also revealed that CrgA regulates the carbon and energy metabolism and that Mcwc-1b is the main, but not the only, target of CrgA.
Uploads
Papers by santiago torres