an rna polymerase iii-dependent heterochromatin barrier at fission yeast centromere 1在裂殖酵母rna聚合酶iii-dependent异染色质障碍着丝粒1.pdfVIP

An RNA Polymerase III-Dependent Heterochromatin Barrier at Fission Yeast Centromere 1 ¤ Kristin C. Scott*, Caroline V. White , Huntington F. Willard Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina, United States of America Heterochromatin formation involves the nucleation and spreading of structural and epigenetic features along the chromatin fiber. Chromatin barriers and associated proteins counteract the spreading of heterochromatin, thereby restricting it to specific regions of the genome. We have performed gene expression studies and chromatin immunoprecipitation on strains in which native centromere sequences have been mutated to study the mechanism by which a tRNAAlanine gene barrier (cen1 tDNAAla) blocks the spread of pericentromeric heterochromatin at the centromere of chromosome 1 (cen1) in the fission yeast, Schizosaccharomyces pombe. Within the centromere, barrier activity is a general property of tDNAs and, unlike previously characterized barriers, requires the association of both transcription factor IIIC and RNA Polymerase III. Although the cen1 tDNAAla gene is actively transcribed, barrier activity is independent of transcriptional orientation. These findings provide experimental evidence for the involvement of a fully assembled RNA polymerase III transcription complex in defining independent structural and functional domains at a eukaryotic centromere. Citation: Scott KC, White CV, Willard HF (2007) An RNA Polymerase III-Dependent Heterochromatin Barrier at Fission Yeast Centromere 1. PLoS ONE 2(10): e1099. doi:10.1371/journal.pone.0001099 INTRODUCTION defects in chromosome segregation during meiosis. Barrier activity is Eukaryo