Transcriptional silencing of Ty1 elements in the RDN1 locus of yeast.
We demonstrate that in Saccharomyces cerevisiae, the tandem array of ribosomal RNA genes (RDN1) is a target for integration of the Ty1 retrotransposon that results in silencing of Ty1 transcription and transposition. Ty1 elements transpose into random rDNA repeat units and are mitotically stable. In addition, we have found that mutation of several putative modifiers of RDN1 chromatin structure abolishes silencing of Ty1 elements in the rDNA array. Disruption of SIR2, which elevates recombination in RDN1, or TOP1, which increases psoralen accessibility in rDNA, or HTA1-HTB1, which reduces histone H2A-H2B levels and causes localized chromatin perturbations, abolishes transcriptional silencing of Ty1 elements in RDN1. Furthermore, deletion of the gene for the ubiquitin conjugating enzyme Ubc2p, which ubiquitinates histones in vitro, derepresses not only Ty1 transcription but also mitotic recombination in RDN1. On the basis of these results, we propose that a specialized chromatin structure exists in RDN1 that silences transcription of the Ty1 retrotransposon.
Bryk
M
M
Molecular Genetics Program, Wadsworth Center and School of Public Health, State University of New York at Albany, 12201-2002, USA.
Banerjee
M
M
Murphy
M
M
Knudsen
K E
KE
Garfinkel
D J
DJ
Curcio
M J
MJ
D001483:Base Sequence; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D006655:Histone Deacetylases; D006657:Histones / Q000378:metabolism; D008025:Ligases / Q000235:genetics; D008938:Mitosis; D008969:Molecular Sequence Data; D012331:RNA, Fungal / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D018626:Retroelements / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic; D044763:Ubiquitin-Conjugating Enzymes
D002843:Chromatin; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006657:Histones; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D018626:Retroelements; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D044763:Ubiquitin-Conjugating Enzymes; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases; D004264:DNA Topoisomerases, Type I; D008025:Ligases