DNA binding protein profiles in Alzheimer's disease

Eleven frozen autopsy specimens from cerebral cortex were tested for DNA-binding protein profiles. Six were Alzheimer's disease (AD) brains, 1 was Parkinson's/senile dementia of the Alzheimer's type and 4 were age-matched control brains. Proteins were extracted in a guanidine thiocyanate-containing solvent and freed of all nucleic acids by density gradient sedimentation. The proteins were separated by sodium dodecyl sulfate gel electrophoresis and transferred to nitrocellulose by electroblotting under conditions which favor renaturation of proteins containing only one type of polypeptide. The nitrocellulose was treated with partially denatured radiolabeled DNA, washed and subjected to autoradiography. An Mr = 43 000 (43 K) DNA-binding protein was detected in 5 of the 6 AD brains and was found to be absent or at least greatly reduced in any of the other 6 brains. No other DNA-binding proteins were found which could be associated with AD brains. The nature of the 43 K protein has yet to be determined.