Tat is a small HIV regulatory protein essential for viral replication whose function is to enhance transcription elongation from the viral promoter. There has been substantial recent progress in the HARC Center on structural studies of Tat and its complexes, most notably Tat bound to P-TEFb and components of the Super Elongation Complex (SEC). However, the transcription process is quite complex and dynamic and it is increasingly clear that many other host factors come into play. In this project, we will: examine ubiquitination of Tat and determine structures of relevant complexes, determine structures of Tat with novel 7SK snRNP host complexes, including newly discovered complexes, and examine connections between 7SK snRNP complexes and the SEC.
Rev is a small HIV regulatory protein essential for viral replication whose function is to export unspliced and partially spliced viral RNAs from the nucleus to the cytoplasm. Rev binds as an oligomer to the RRE RNA. To date, we have determined a high-resolution crystal structure of the Rev dimer, a co-crystal structure of the Rev dimer bound to RRE RNA, and have assembled well-defined nuclear export complexes with Crm1/RanGTP. A high-resolution structure of the entire export complex is within reach. We will determine the high-resolution structure of Rev-RRE/Crm1 complexes as well as study roles of alternative RNA conformations in assembling Rev-RRE export complexes, characterize novel host protein interactions with Rev, and examine the evolution of Rev overlapping reading frames, and examine RRE RNA structure in vivo by 3-D mapping.