IDENTIFICATION OF THE PROMOTER REGION OF CHICKEN ANEMIA VIRUS (CAV) CONTAINING A NOVEL ENHANCER-LIKE ELEMENT

The single promoter region in the cloned genome [Noteborn et al., J, V irol, 65 (1991) 3131-3139] of chicken anemia virus (CAV) in chicken T- cells was analysed via CAT assays. A unique region containing four or five near-perfect direct repeats (DR) of 21 bp with one 12-bp insert w as proven to be the main transcription-activation element, with enhanc erlike characteristics. PCR studies revealed that CAV isolates from ac ross the world all contained this promoter sequence. Electrophoretic m obility-shift assays (EMSA) showed that individual DR units, as well a s the 12-bp insert, can bind to nuclear factors of chicken T-cells. Co mpetition assays revealed that the DR units bound to factors other tha n the 12-bp insert. A synthetic oligodeoxyribonucleotide containing an SP1-box (5'-GGGCGG) could compete with factors binding to the 12-bp i nsert. Purified human SP1 was shown to have very strong affinity for t he 12-bp insert.