A role for TFIIIC transcription factor complex in genome organization.
Eukaryotic genome complexity necessitates boundary and insulator elements to partition genomic content into distinct domains. We show that inverted repeat (IR) boundary elements flanking the fission yeast mating-type heterochromatin domain contain B-box sequences, which prevent heterochromatin from spreading into neighboring euchromatic regions by recruiting transcription factor TFIIIC complex without RNA polymerase III (Pol III). Genome-wide analysis reveals TFIIIC with Pol III at all tRNA genes, many of which cluster at pericentromeric heterochromatin domain boundaries. However, a single tRNA(phe) gene with modest TFIIIC enrichment is insufficient to serve as boundary and requires RNAi-associated element to restrain heterochromatin spreading. Remarkably, we found TFIIIC localization without Pol III at many sites located between divergent promoters. These sites appear to act as chromosome-organizing clamps by tethering distant loci to the nuclear periphery, at which TFIIIC is concentrated into several distinct bodies. Our analyses uncover a general genome organization mechanism involving conserved TFIIIC complex.
Noma
Ken-ichi
K
Laboratory of Molecular Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Cam
Hugh P
HP
Maraia
Richard J
RJ
Grewal
Shiv I S
SI
D002875:Chromosomes / Q000235:genetics; D004258:DNA Polymerase III / Q000235:genetics; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D016681:Genome, Fungal / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference / Q000502:physiology; D012343:RNA, Transfer / Q000235:genetics; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism; D019474:Transcription Factors, TFIII / Q000235:genetics*; D000098832:Transcription Factor TFIIIC
D006570:Heterochromatin; D019474:Transcription Factors, TFIII; D000098832:Transcription Factor TFIIIC; D012343:RNA, Transfer; D004258:DNA Polymerase III