Cell cycle roles for GCN5 revealed through genetic suppression.

The conserved acetyltransferase Gcn5 is a member of several complexes in eukaryotic cells, playing roles in regulating chromatin organization, gene expression, metabolism, and cell growth and differentiation via acetylation of both nuclear and cytoplasmic proteins. Distinct functions of Gcn5 have been revealed through a combination of biochemical and genetic approaches in many in vitro studies and model organisms. In this review, we focus on the unique insights that have been gleaned from suppressor studies of gcn5 phenotypes in the budding yeast Saccharomyces cerevisiae.

Connecting GCN5's centromeric SAGA to the mitotic tension-sensing checkpoint.

Multiple interdependent mechanisms ensure faithful segregation of chromosomes during cell division. Among these, the spindle assembly checkpoint monitors attachment of spindle microtubules to the centromere of each chromosome, whereas the tension-sensing checkpoint monitors the opposing forces between sister chromatid centromeres for proper biorientation. We report here a new function for the deeply conserved Gcn5 acetyltransferase in the centromeric localization of Rts1, a key player in the tension-sensing checkpoint.

Promotion of Cell Viability and Histone Gene Expression by the Acetyltransferase Gcn5 and the Protein Phosphatase PP2A in Saccharomyces cerevisiae.

Histone modifications direct chromatin-templated events in the genome and regulate access to DNA sequence information. There are multiple types of modifications, and a common feature is their dynamic nature. An essential step for understanding their regulation, therefore, lies in characterizing the enzymes responsible for adding and removing histone modifications.

Different roles for Aurora B in condensin targeting during mitosis and meiosis.

Condensin complexes are essential for mitotic and meiotic chromosome segregation. Caenorhabditis elegans, like other metazoans, has two distinct mitotic and meiotic condensin complexes (I and II), which occupy distinct chromosomal domains and perform non-redundant functions. Despite the differences in mitotic and meiotic chromosome behavior, we uncovered several conserved aspects of condensin targeting during these processes.

Restricting dosage compensation complex binding to the X chromosomes by H2A.Z/HTZ-1.

Dosage compensation ensures similar levels of X-linked gene products in males (XY or XO) and females (XX), despite their different numbers of X chromosomes. In mammals, flies, and worms, dosage compensation is mediated by a specialized machinery that localizes to one or both of the X chromosomes in one sex resulting in a change in gene expression from the affected X chromosome(s). In mammals and flies, dosage compensation is associated with specific histone posttranslational modifications and replacement with variant histones.

The worm solution: a chromosome-full of condensin helps gene expression go down.

Dosage compensation in the nematode Caenorhabditis elegans is achieved by the binding of a condensin-like dosage compensation complex (DCC) to both X chromosomes in hermaphrodites to downregulate gene expression two-fold. Condensin I(DC), a sub-part of the DCC, differs from the mitotic condensin I complex by a single subunit, strengthening the connection between dosage compensation and mitotic chromosome condensation. The DCC is targeted to X chromosomes by initial binding to a number of recruiting elements, followed by dispersal or spreading to secondary sites.

Large P body-like RNPs form in C. elegans oocytes in response to arrested ovulation, heat shock, osmotic stress, and anoxia and are regulated by the major sperm protein pathway.

As Caenorhabditis elegans hermaphrodites age, sperm become depleted, ovulation arrests, and oocytes accumulate in the gonad arm. Large ribonucleoprotein (RNP) foci form in these arrested oocytes that contain RNA-binding proteins and translationally masked maternal mRNAs. Within 65 min of mating, the RNP foci dissociate and fertilization proceeds.