Position-effect variegation in Drosophila: the modifier Su(var)3-7 is a modular DNA-binding protein.
An increase in the dose of the Su(var)3-7 locus of Drosophila augments heterochromatin-promoted variegated silencing. The deduced protein sequence of Su(var)3-7 reveals seven widely spaced zinc fingers. We found that Su(var)3-7 has affinity for DNA in vitro and that the minimal protein sequence requirement for DNA binding is any module containing two zinc fingers and the interval between them. As Su(var)3-7 is a heterochromatin-associated protein, we tested its affinity for various satellite DNA sequences in vitro. The AATAT and 353-bp elements have the highest affinity. If affinity for satellite DNAs contributes to the presence of Su(var)3-7 in heterochromatin, a general affinity for DNA, or sequences yet to be determined, suggests a function in the genomic silencing of position-effect variegation: expansion of heterochromatin, whether continuous by spreading or discontinuous by pairing with sequence elements scattered through euchromatin, could use the affinity of Su(var)3-7 for DNA.
Cléard
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F
Department of Zoology and Animal Biology, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Spierer
P
P
D020856:AT Rich Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D016384:Consensus Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004276:DNA, Satellite / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D023061:Gene Order / Q000235:genetics*; D017344:Genes, Insect / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics; D016335:Zinc Fingers
D004276:DNA, Satellite; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C449619:Su(var)3-7 protein, Drosophila; D004247:DNA