Dr. Schlesinger is renowned for his work on heat-shock proteins, on protein modification and on the assembly of small RNA enveloped viruses. In 1978, he discovered the first examples in vertebrate cells of heat-shock proteins, which cells produce when their normal proteins unfold as a result of high temperature or other stressful conditions. Many heat-shock proteins act to refold the damaged proteins, helping the cell survive. He also uncovered the first example in nonbacterial cells of a virus glycoprotein that can be modified by the addition of a fatty acid group and showed that this modification occurs in many cellular proteins associated with cell membranes. In the virus, the addition of fatty acids is important in effecting the final stages in the replication of the virus particle and allows for efficient assembly in which the RNA-containing virus core interacts with the cell's membranes and leads to budding and release of newly formed progeny virus. In his most recent work, he utilized molecular genetics to analyze protein-protein interactions in virus assembly and budding.