The ribosomal RNA (rRNA) genes of Drosophila melanogaster can undergo a disproportionate replication of their number. This occurs when the cluster of rRNA genes (rDNA) of one chromosome is maintained with a homologous chromosome that is completely or partially deficient in its rDNA. Under appropriate genetic conditions, it appears that disproportionate rDNA replication can be generated at the l...

Restriction fragment length polymorphism (RFLP) analysis was performed on the internal transcribed spacer regions of 204 Sporothrix schenckii isolates and on one strain each of the related fungi, S. schenckii var. luriei, S. curviconia, S. inflata and Ceratocystis stenoceras. S. schenckii isolates, which have been collected from around the world, have already been typed according to their mitoc...

Among acetyltransferases, the MYST family enzyme Esa1p is distinguished for its essential function and contribution to transcriptional activation and DNA double-stranded break repair. Here we report that Esa1p also plays a key role in silencing RNA polymerase II (Pol II)-transcribed genes at telomeres and within the ribosomal DNA (rDNA) of the nucleolus. These effects are mediated through Esa1p...

Mitotic cell division involves the equal segregation of all chromosomes during anaphase. The presence of ribosomal DNA (rDNA) repeats on the right arm of chromosome XII makes it the longest in the budding yeast genome. Previously, we identified a stage during yeast anaphase when rDNA is stretched across the mother and daughter cells. Here, we show that resolution of sister rDNAs is achieved by ...

The ribosomal DNA (rDNA) of eukaryotes is organized as large tandem arrays. Here, we compare the genomic locations of rDNA among yeast species and show that, despite its huge size (>1 Mb), the rDNA array has moved around the genome several times within the family Saccharomycetaceae. We identify an ancestral, nontelomeric, rDNA site that is conserved across many species including Saccharomyces c...

Detailed karyotypes of 4 lily species (Lilium regale, L. duchartrei, L. brownii var viridium and L. leucanthum var. centifolium), native to Qinling Moutains in China, were constructed on the basis of chromosome arm lengths and fluorescence in situ hybridisation (FISH) with the 45S and 5S rDNA sequences as probes. Results showed that the relative length of these 4 genomes were all around 300μm, ...

Intraand interspecific variation of the nu­ clear ribosomal internal transcribed spacers (ITS) of 77 Smittium isolates and related genera was studied using RFLP. Due to the sequence and length varia­ tion encountered, the ITS is unsuitable for compar­ ison at the species level within Smittium, as presently delimited. Intraand interspecific variation of 18S rDNA was also analyzed. Cladistic anal...

The Rif1 protein is a negative regulator of DNA replication initiation in eukaryotes. Here we show that budding yeast Rif1 inhibits DNA replication initiation at the rDNA locus. Absence of Rif1, or disruption of its interaction with PP1/Glc7 phosphatase, leads to more intensive rDNA replication. The effect of Rif1-Glc7 on rDNA replication is similar to that of the Sir2 deacetylase, and the two ...

The pattern and frequency of insertions that enable transposable elements to remain active in a population are poorly understood. The retrotransposable element R2 exclusively inserts into the 28S rRNA genes where it establishes long-term, stable relationships with its animal hosts. Previous studies with laboratory stocks of Drosophila simulans have suggested that control over R2 retrotransposit...