A novel neuron-specific DNA end-binding factor in the murine brain

To characterize the distribution of transcription factor AP-1 and YY1 DNA-b inding activities in the rat brain, the labeled target oligonucleotides wer e loaded on brain sections and after incubation and washing, the residual s ignal was registered by autoradiography. The binding was predominantly asso ciated with neurons and was regionally specific with highest levels in the cerebellum, hippocampus, and piriform cortex. The identified binding factor was not, however, sequence-specific, but apparently recognized DNA ends an d was activated by long double-stranded DNA. UV cross-linking identified th e molecular mass of the factor to be about 80 kDa. The factor was not found in soluble brain extracts, suggesting its association with membranes or th e nuclear matrix. Despite apparent similarities with Ku protein, which targ ets DNA-ends, the DNA end-binding activity was present in brains of Ku86- a nd Ku70-deficient mice. Since DNA end-binding factors are generally involve d in DNA repair, the same function may be suggested for the novel factor id entified in the present study.