BIOLOGICAL-ACTIVITY AND INTRACELLULAR LOCATION OF THE TAT PROTEIN OF EQUINE INFECTIOUS-ANEMIA VIRUS

The Tat protein of equine infectious anemia virus (EIAV) was synthesiz ed in Escherichia coli using the inducible expression plasmid, pET16b, which contains a His.Tag leader, thus allowing for rapid and efficien t enrichment of the histidine-tagged protein by metal affinity chromat ography. Yields of up to 20 mg of Tat were obtained from 10(11) bacter ial cells. The recombinant Tat protein was shown to potently trans-act ivate the EIAV long terminal repeat (LTR) following its introduction i nto canine cells by 'scrape loading'. The EIAV Tat protein was found t o localize predominantly within the cytoplasm, in contrast to HIV-1 Ta t. The availability of large amounts of purified functional EIAV Tat p rotein should greatly facilitate detailed structure-function analyses.