Base composition and nucleosomal organization of the Schizosaccharomyces pombe genome

Base composition and nucleosomal organization of the Schizosaccharomyces pombe genome

Luis Quintales, Ignacio Soriano, Enrique Vázquez, Francisco Antequera*

Instituto de Biología Funcional y Genómica
Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca
Campus Miguel de Unamuno
37007-Salamanca. Spain

Nucleosomes are the basic units of chromatin. They facilitate the packaging of the eukaryotic genome inside the nucleus and modulate the access of regulatory proteins to DNA either directly or through the epigenetic modification of histones. To study the contribution of nucleosomes to genome regulation in S. pombe, we have generated high-resolution maps that allow precise localisation of individual nucleosomes. Our results show that regular nucleosomal arrays extend upstream from the nucleosome depleted region present at the 5’ end of many genes and downstream from the transcription termination site. Nucleosome positioning is also present along genes that show low or undetectable levels of transcription. Different patterns are obtained depending on whether the genomic position used to generate the aggregated nucleosomal profiles is localized inside the transcribed units or at their 5’ or 3’ end. These results indicate that regular nucleosomal arrays are

widespread along the genome and do not necessarily represent a specific feature of the 5’ end of the genes. We have also found that the nucleosomal profile overlaps with periodic oscillations in the A+T content of the underlying DNA sequence, which suggests a stable association between nucleosomes and some specific regions of DNA. The implications of these observations for the organization and the evolution of the genome will be discussed.

Keywords:
Presented by: Antequera, Francisco
Presentation type: Invited speaker
Session: DNA metabolism, chromatin, gene expression