RUN-ON GENE-TRANSCRIPTION IN HUMAN NEOCORTICAL NUCLEI - INHIBITION BYNANOMOLAR ALUMINUM AND IMPLICATIONS FOR NEURODEGENERATIVE DISEASE

The incorporation of [alpha-P-32]-uridine triphosphate into DNA transc ription products was examined in short post-mortem interval (PMI) huma n brain neocortical nuclei (n, 22; PMI, 0.5-24 h) using run-on gene tr anscription. Reverse Northern dot-blot hybridization of newly synthesi zed RNA against either total cDNA or Alu repetitive DNA indicated that human brain neocortical nuclei of up to 4-h PMI were efficient in inc orporating radiolabel into new transcription products, after which the re was a graded decline in de novo RNA biosynthetic capacity. To test the effects of 0-3000 nM concentrations of ambient aluminum on RNA pol ymerase I (RNAP I) and RNA polymerase II (RNAP II) transcription, dot blots containing 0.5, 1.0, 2.0, and 5.0 mu g of DNA for (1) the human- specific Alu repetitive element (2) the neurofilament light (NFL) chai n, and (3) glial fibrillary acidic protein (GFAP) were Northern hybrid ized against newly synthesized radiolabeled total RNA. These DNAs repr esent heterogeneous nuclear RNA (hnRNA), neuronal-, and glial-specific markers, respectively. We report here a dose-dependent repression in the biosynthetic capabilities of brain RNAP II in the range of 50-100 nM aluminum, deficits similar to those previously described using a ra bbit neocortical nuclei transcription system and at concentrations tha t have been reported in Alzheimer's disease (AD) euchromatin. Transcri ption from RNAP II and the neuron-specific NFL gene in the presence of aluminum was found to be particularly affected. These findings suppor t the hypothesis that brain gene transcription in the presence of trac e amounts of ambient aluminum impairs mammalian brain DNA to adequatel y read out genetic information.