Binding of DNA to alpha/beta-type small, acid-soluble proteins from spores of Bacillus or Clostridium species prevents formation of cytosine dimers, cytosine-thymine dimers, and bipyrimidine photoadducts after UV irradiation.
Small, acid-soluble proteins (SASP) of the alpha/beta-type from spores of Bacillus and Clostridium species bind to DNA; this binding prevents formation of cyclobutane-type thymine dimers upon UV irradiation, but promotes formation of the spore photoproduct, an adduct between adjacent thymine residues. alpha/beta-Type SASP also bound to poly(dG).poly(dC) and poly(dA-dG).poly(dC-dT). While UV irradiation of poly(dG).poly(dC) produced cyclobutane-type cytosine dimers as well as fluorescent bipyrimidine adducts, the yields of both types of photoproduct were greatly reduced upon irradiation of alpha/beta-type SASP-poly(dG).poly(dC) complexes. UV irradiation of poly(dA-dG).poly(dC-dT) produced a significant amount of a cyclobutane dimer between cytosine and thymine, as well as a 6-4 bipyrimidine adduct. Again, binding of alpha/beta-type SASP to poly(dA-dG).poly(dC-dT) greatly reduced formation of these two photoproducts, although formation of the cytosine-thymine analog of the spore photoproduct was not observed. These data provide further evidence for the dramatic change in DNA structure and photoreactivity which takes place on binding of alpha/beta-type SASP and suggest that binding of these proteins to DNA in vivo prevents formation of most deleterious photoproducts upon UV irradiation.
Fairhead
H
H
Department of Biochemistry, University of Connecticut Health Center, Farmington 06030.
Setlow
P
P
D001407:Bacillus / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D003013:Clostridium / Q000378:metabolism*; D003503:Cyclobutanes; D004249:DNA Damage / Q000528:radiation effects*; D011089:Polydeoxyribonucleotides / Q000378:metabolism; D011740:Pyrimidine Dimers; D012808:Sigma Factor; D014157:Transcription Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*
D001426:Bacterial Proteins; D003503:Cyclobutanes; D011089:Polydeoxyribonucleotides; D011740:Pyrimidine Dimers; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; C016681:poly(dG).poly(dC); C044165:poly(d(G-T).d(C-A))