GLIAL AND MUSCLE EMBRYONAL CARCINOMA CELL-SPECIFIC INDEPENDENT REGULATION OF EXPRESSION OF HUMAN JC-VIRUS EARLY PROMOTER BY CYCLIC-AMP RESPONSE ELEMENTS AND ADJACENT NUCLEAR FACTOR-1 BINDING-SITES

The human polyoma JC virus (JCV) is a glial cell-specific virus and is the etiological agent for the terminal AIDS-associated brain disease, progressive multifocal leukoencephalopathy (PML). JCV contains severa l binding sites for transcriptional factors that are important for act ivity in glial cells, including cyclic AMP (cAMP) response elements (C REs) which are four nucleotides from nuclear factor 1 (NF1) sites with in the two 98 bp repeat regions, We studied the combined role of cAMP and NF1 in regulating the expression of the JCV early promoter-enhance r (JCV(E)) in differentiating glial and muscle P19 embryonal carcinoma cells. JCV(E) expression remained several-fold higher in the presence of cAMP in glial cells, irrespective of whether the relatively strong activity of JCV(E) was greatly reduced by NF1 site mutations. In cont rast, cAMP had no effect in muscle cells, independent of whether the m odest activity of JCV(E) was two-fold higher due to NF1 site mutations , The in vivo effects were confirmed with in vitro transcription assay s using glial cell extracts, competitors of CRE, and the NF1 site, and single repeat JCV(E) region with mutations in the NF1 II/III binding sites as templates. The in vitro results also indicated that the effec ts were due to the CREs of JCV, rather than to the indirect effects of cAMP, Overall, the results indicated that NF1 and cAMP have independe nt, different, tissue-specific, and direct effects in the regulation o f JCV(E), These effects may contribute the neurotropic PML-inducing pa ttern of expression of JCV(E). (C) 1996 Wiley-Liss, Inc.