Neither Reb1p nor poly(dA*T) elements are responsible for the highly specific chromatin organization at the ILV1 promoter.
Analysis of the chromatin structure at the yeast ILV1 locus revealed highly positioned nucleosomes covering the entire locus except for a hypersensitive site in the promoter region. All previously identified cis-acting elements required for GCN4-independent ILV1 basal level transcription, including a binding site for the REB1 protein (Reb1p), and a poly(dA*dT) element (26 As out of 32 nucleotides) situated 15 base pairs downstream of the Reb1p-binding site, reside within this hypersensitive site. The existence of a second A*T-rich element (25 As out of 33 nucleotides) present six base pairs upstream of the Reb1p-binding site, suggested that nucleosome exclusion from the hypersensitive site in the ILV1 promoter region might be dictated by synergistic action of the two poly(dA*dT) elements. Replacing one or both of them had, however, no effect on the chromatin structure of the ILV1 promoter, although drastically reduced basal transcription. Similarly, deletion of the Reb1p-binding site, albeit affecting ILV1 expression, had no detectable effect on chromatin at the ILV1 promoter. The absence of a good correlation between effects of these elements on gene activity and on chromatin structure at the ILV1 promoter indicates that the chromatin organization present at the ILV1 promoter is independent of the known regulatory elements and most likely dictated directly by the DNA sequence.
Moreira
José M A
JM
Department of Genetics, Institute of Molecular Biology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353, Copenhagen K, Denmark.
Hörz
Wolfram
W
Holmberg
Steen
S
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002843:Chromatin / Q000235:genetics* / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003850:Deoxyribonuclease I; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010957:Plasmids; D011067:Poly dA-dT / Q000235:genetics*; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D014157:Transcription Factors; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; C065681:REB1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D011067:Poly dA-dT; C080946:IlvI protein, Bacteria; D003850:Deoxyribonuclease I