TRANSCRIPTION OF A HUMAN NEUROTROPIC VIRUS PROMOTER IN GLIAL-CELLS - EFFECT OF YB-1 ON EXPRESSION OF THE JC VIRUS LATE GENE

We have isolated a partial recombinant cDNA clone from a HeLa expressi on library which encodes a protein capable of binding to the central r egion of the human neurotropic JC virus (JCV) enhancer/promoter, terme d the B region. Sequence analysis revealed a complete homology of the partial cDNA clone to the N-terminal region of a previously described DNA-binding protein, termed YB-1. Band shift analyses have indicated t hat the bacterially produced YB-1 interacts specifically with the doub le-stranded B oligonucleotide as well as the corresponding single-stra nded DNA fragment representing the early promoter sequence. Further an alysis indicated that the YB-1 protein binds specifically to the C/T-r ich sequence of the B domain, which is located in close proximity to t he TATA box within the virus enhancer/promoter. Results from cotransfe ction experiments demonstrated that the full-length (YB-1) but not the partial cDNA enhances expression of the JCV late (JCV(L)) promoter in glial cells. Cointroduction into glial cells of a recombinant express ing the YB-1 and JCV(L) deletion mutants indicated that removal of the C/T-rich sequence of the B domain reduces the level of activation of the virus promoter by YB-1. Further cotransfection experiments reveale d that the virus transactivating protein T antigen appears to diminish the ability of YB-1 to activate JCV(L) gene expression. RNA studies i ndicated that YB-1 is expressed in several cell types and tissues. Exa mination of YB-1 RNA from mouse brain at various stages of development revealed high levels of YB-1 RNA at early stages of development and l ower levels at all subsequent developmental stages.