Activation of Prp28 ATPase by phosphorylated Npl3 at a critical step of spliceosome remodeling.

Splicing, a key step in the eukaryotic gene-expression pathway, converts precursor messenger RNA (pre-mRNA) into mRNA by excising introns and ligating exons. This task is accomplished by the spliceosome, a macromolecular machine that must undergo sequential conformational changes to establish its active site. Each of these major changes requires a dedicated DExD/H-box ATPase, but how these enzymes are activated remain obscure.

Sex alters molecular evolution in diploid experimental populations of S. cerevisiae.

Sex is common among eukaryotes, but entails considerable costs. The selective conditions that drive the evolutionary maintenance of sexual reproduction remain an open question. One long-standing explanation is that sex and recombination facilitate adaptation to fluctuating environmental conditions, although the genetic mechanisms that underlie such a benefit have not been empirically observed.

Abundant and diverse Tetrahymena species living in the bladder traps of aquatic carnivorous Utricularia plants.

Ciliates are unicellular eukaryotes known for their cellular complexity and wide range of natural habitats. How they adapt to their niches and what roles they play in ecology remain largely unknown. The genus Tetrahymena is among the best-studied groups of ciliates and one particular species, Tetrahymena thermophila, is a well-known laboratory model organism in cell and molecular biology, making it an excellent candidate for study in protist ecology.

Adaptive transcription-splicing resynchronization upon losing an essential splicing factor.

Essential genes form the core of a genome and are therefore thought to be indispensable for cellular viability. However, recent findings have challenged this notion in that cells may survive in the absence of some essential genes provided that relevant genetic modifiers are in existence. We therefore hypothesized that the loss of an essential gene may not always be fatefully detrimental; instead, it may pave the way towards genome evolution.

The conserved AU dinucleotide at the 5' end of nascent U1 snRNA is optimized for the interaction with nuclear cap-binding-complex.

Splicing is initiated by a productive interaction between the pre-mRNA and the U1 snRNP, in which a short RNA duplex is established between the 5' splice site of a pre-mRNA and the 5' end of the U1 snRNA. A long-standing puzzle has been why the AU dincucleotide at the 5'-end of the U1 snRNA is highly conserved, despite the absence of an apparent role in the formation of the duplex. To explore this conundrum, we varied this AU dinucleotide into all possible permutations and analyzed the resulting molecular consequences.

A population study of killer viruses reveals different evolutionary histories of two closely related Saccharomyces sensu stricto yeasts.

Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted killer toxins by yeast cells through acquiring double-stranded RNA viruses is one such prominent example. Although the killer behaviour has been well studied in laboratory yeast strains, our knowledge regarding how killer viruses are spread and maintained in nature and how yeast cells co-evolve with viruses remains limited.

Functions of the DExD/H-box proteins in nuclear pre-mRNA splicing.

In eukaryotes, many genes are transcribed as precursor messenger RNAs (pre-mRNAs) that contain exons and introns, the latter of which must be removed and exons ligated to form the mature mRNAs. This process is called pre-mRNA splicing, which occurs in the nucleus. Although the chemistry of pre-mRNA splicing is identical to that of the self-splicing Group II introns, hundreds of proteins and five small nuclear RNAs (snRNAs), U1, U2, U4, U5, and U6, are essential for executing pre-mRNA splicing.

Dynamic large-scale chromosomal rearrangements fuel rapid adaptation in yeast populations.

Large-scale genome rearrangements have been observed in cells adapting to various selective conditions during laboratory evolution experiments. However, it remains unclear whether these types of mutations can be stably maintained in populations and how they impact the evolutionary trajectories. Here we show that chromosomal rearrangements contribute to extremely high copper tolerance in a set of natural yeast strains isolated from Evolution Canyon (EC), Israel.

The evolution of low mutation rates in experimental mutator populations of Saccharomyces cerevisiae.

Mutation is the source of both beneficial adaptive variation and deleterious genetic load, fueling the opposing selective forces than shape mutation rate evolution. This dichotomy is well illustrated by the evolution of the mutator phenotype, a genome-wide 10- to 100-fold increase in mutation rate. This phenotype has often been observed in clonally expanding populations exposed to novel or frequently changing conditions.

A tradeoff drives the evolution of reduced metal resistance in natural populations of yeast.

Various types of genetic modification and selective forces have been implicated in the process of adaptation to novel or adverse environments. However, the underlying molecular mechanisms are not well understood in most natural populations. Here we report that a set of yeast strains collected from Evolution Canyon (EC), Israel, exhibit an extremely high tolerance to the heavy metal cadmium.

Heterothallism in Saccharomyces cerevisiae isolates from nature: effect of HO locus on the mode of reproduction.

Understanding the evolution of sex and recombination, key factors in the evolution of life, is a major challenge in biology. Studies of reproduction strategies of natural populations are important to complement the theoretical and experimental models. Fungi with both sexual and asexual life cycles are an interesting system for understanding the evolution of sex.

Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates the expression of PACAP in cultured tilapia astrocytes.

Neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic hormone that is involved in numerous physiologic functions. The present study examines the presence and the functional significance of PACAP and its receptor in the brain and astrocytes of tilapia (Oreochromis mossambicus). This is the first demonstration of the full-length nucleotide sequence of tPACAP gene in tilapia pituitary, brain, and cultured astrocytes.