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Formins are involved in diverse aspects of morphogenesis, and share two regions of homology: FH1 and FH2. We describe a new formin homology region, FH3. FH3 is an amino-terminal domain that differs from the Rho binding site identified in Bni1p and p140mDia. The Schizosaccharomyces pombe formin Fus1 is required for conjugation, and is localized to the(More)
Cullin-4 forms a scaffold for multiple ubiquitin ligases. In Schizosaccharomyces pombe, the Cullin-4 homologue (Pcu4) physically associates with Ddb1 and the COP9 signalosome (CSN). One target of this complex is Spd1. Spd1 regulates ribonucleotide reductase (RNR) activity. Spd1 degradation during S phase, or following DNA damage of G2 cells, results in the(More)
The human UV-damaged DNA-binding protein Ddb1 associates with cullin 4 ubiquitin ligases implicated in nucleotide excision repair (NER). These complexes also contain the signalosome (CSN), but NER-relevant ubiquitination targets have not yet been identified. We report that fission yeast Ddb1, Cullin 4 (Pcu4), and CSN subunits Csn1 and Csn2 are required for(More)
Activation of oncogenes or inhibition of WEE1 kinase deregulates cyclin-dependent kinase (CDK) activity and leads to replication stress; however, the underlying mechanism is not understood. We now show that elevation of CDK activity by inhibition of WEE1 kinase rapidly increases initiation of replication. This leads to nucleotide shortage and reduces(More)
Investigations into sexual differentiation and pheromone response in the fission yeast Schizosaccharomyces pombe are complicated by the need to first starve the cells of nitrogen. Most mating-related experiments are therefore performed on non-dividing cells. Here we overcome this problem by using two mutants that bypass the nutritional requirements and(More)
Fission yeast cells undergo sexual differentiation in response to nitrogen starvation. In this process haploid M and P cells first mate to form diploid zygotes, which then enter meiosis and sporulate. Prior to mating, M and P cells communicate with diffusible mating pheromones that activate a signal transduction pathway in the opposite cell type. The(More)
Eukaryotic cells normally differentiate from G(1); here we investigate the mechanism preventing expression of differentiation-specific genes outside G(1). In fission yeast, induction of the transcription factor Ste11 triggers sexual differentiation. We find that Ste11 is only active in G(1) when Cdk activity is low. In the remaining part of the cell cycle,(More)
Mating-type switching in the fission yeast, S. pombe, is initiated by a DNA double-strand break (DSB) between the mat1 cassette and the H1 homology box. The mat1-cis-acting mutant, smt-0, abolishes mating-type switching and is shown here to be a 263-bp deletion. This deletion starts in the middle of the H1 homology box, 31 bp from the site of the DSB, and(More)
The fission yeast, Schizosaccharomyces pombe, expresses one of two alternative mating types. They are specified by one of two determinants (M or P) present at the mat1 locus. In addition, silent copies of M and P are present on the same chromosome. In the present work we demonstrate that the difference between the active and the silent stage of the P(More)
DNA replication is an extremely accurate process and cells have evolved intricate control mechanisms to ensure that each region of their genome is replicated only once during S phase. Here, we compare what is known about the processes that prevent re-replication in prokaryotic and eukaryotic cells by using the model organisms Escherichia coli and(More)