INCREASED CELLULAR UPTAKE OF THE HUMAN IMMUNODEFICIENCY VIRUS-1 TAT PROTEIN AFTER MODIFICATION WITH BIOTIN

The human immunodeficiency virus-1 Tat protein can efficiently enter c ells when added exogenously in tissue culture. Using the transactivati on activity of Tat as a measure of intracellular delivery, we found th at the addition of hydrophobic groups to Tat potentiated its uptake. B iotin was the most promising of the reagents tested and we characteriz ed this effect in more detail. When coupled through a cysteine thiol, the addition of a single biotin to Tat increased activity by about six fold. Increased activity was only seen with reducible biotin analogs, as modification with noncleavable analogs is known to block Tat transa ctivation activity. Biotin had no effect on Tat uptake when mixed with Tat without cross-linking. Recently, Tat was used as a carrier to dir ect the uptake of heterologous proteins into cells. We have used RNase as a model system for studying Tat-mediated uptake and found that bio tin also increased the delivery of a Tat(37-58)-RNase conjugate. The i ncreased uptake of Tat and Tat conjugates by addition of hydrophobic g roups may significantly enhance the usefulness of Tat as a delivery ve hicle, and the approach may be applicable to other systems. (C) 1995 A cademic Press, Inc.