Functional interactions of human immunodeficiency virus type 1 integrase with human and yeast HSP60

Integration of human immunodeficiency virus type 1 (HIV-1) proviral DNA in the nuclear genome is catalyzed by the retroviral integrase (IN). In additi on to IN, viral and cellular proteins associated in the high-molecular-weig ht preintegration complex have been suggested to be involved in this proces s. In an attempt to define host factors interacting with IN, we used an in vitro system to identify cellular proteins in interaction with HIV-1 IN. Th e yeast Saccharomyces cerevisiae was chosen since (i) its complete sequence has been established and the primary structure of all the putative protein s from this eucaryote has been deduced, (ii) there is a significant degree of homology between human and yeast proteins, and (iii) we have previously shown that the expression of HIV-1 IN in yeast induces a lethal phenotype. Strong evidences suggest that this lethality is linked to IN activity in in fected human cells where integration requires the cleavage of genomic DNA. Using IN-affinity chromatography we identified four yeast proteins interact ing with HIV-1 IN, including the yeast chaperonin yHSP60, which is the coun terpart of human hHSP60. Yeast lethality induced by HIV-1 IN was abolished when a mutated HSP60 was coexpressed, therefore suggesting that both protei ns interact in vivo. Besides interacting with HIV-1 IN, the hHSP60 was able to stimulate the in vitro processing and joining activities of IN and prot ected this enzyme from thermal denaturation. In addition, the functional hu man HSP60-HSP10 complex in the presence of ATP was able to recognize the HI V-1 IN as a substrate.