The Tat protein of HIV-1 induces galectin-3 expression

Animal lectins play important roles in a variety of biological processes vi a their recognition of glycoconjugates. Galectin-3 is a beta-galactoside-bi nding lectin whose expression is associated with various pathological proce sses including human T lymphotropic virus (HTLV)-I-infection of human T cel l lines and human immunodeficiency virus (HIV) infection of T-lymphoblastic Molt-3 cell line. In the case of HIV-infected cells, it has been suggested that the increase in galectin-3 expression could be related to the express ion of the viral regulatory gene tat. These results prompt us to perform mo re extensive analyses of the relationship between galectin-3 and HIV-1 Tat expressions. In this study, we found that Tat protein expression induces an upregulation of galectin-3 in several human cell lines. In cotransfection experiments, the 5'-regulatory sequences of the galectin-3 gene were signif icantly upregulated by expression vectors encoding the Tat protein. Analysi s performed with 5'-regulatory deleted sequences suggested that galectin-3 induction by Tat is dependent on activation of the Sp-1 binding transcripti on factor.