Objectives of this proposal are: 1. To determine the structure of the cis-acting regulatory sequences in the HTLV-III LTR that respond to virus-induced trans-acting regulatory factors. HTLV-III enhancers, promoters and positive as well as negative regulatory sequences will be investigated. 2. Analysis of the sequences in the HTLV-III genome that encode the signals that induce the trans-acting regulatory factors in HTLV-III infected cells. Insertion/deletion mutants in an infectious HTLV-III provirus will be made. Vectors designed to express the virally encoded proteins singly or in groups will be made. 3. The proteins encoded by the HTLV-III genome will be investigated using antisera raised to synthetic peptides and to proteins produced by open reading frame expression vectors. Emphasis will be placed on detection of proteins that might be encoded by the SOR, env-lor, and 3' orf regions. 4. Characterization of HTLV-III encoded mRNA species. Donor-acceptor sites of mRNA splicing will be mapped, cDNA libraries will be constructed, and the coding capacity of the cDNA mRNAs determined. 5. The effect of HTLV-III infection on the expression of host genes will be investigated. Studies will include investigation of alterations in the regulation of mRNA corresponding to the IL1, IL2, IL2 receptor and T-cell receptor genes, investigation of the abundance of certain protooncogene sequences (c-myc, c-myb, c-fos). Libraries of cDNA will be prepared that contain sequences corresponding to genes that are either positively or negatively regulated upon HTLV-III infection.