Poster abstracts
Poster number 56 submitted by Niyati Jain
Solution Structure of the HIV-1 Intronic Splicing Silencer and its Interaction with the UP1 Domain of hnRNP A1
Niyati jain (Department of Chemistry, Case Western Reserve University, Cleveland, Ohio), Christopher E. Morgan (Department of Chemistry, Case Western Reserve University, Cleveland, Ohio), Brittany D. Rife (Department of Pathology, Immunology and Laboratory Medicine University of Florida Gainesville, Florida), Marco Salemi (Department of Pathology, Immunology and Laboratory Medicine University of Florida Gainesville, Florida), Blanton S. Tolbert (Department of Chemistry, Case Western Reserve University, Cleveland, Ohio)
Abstract:
Alternative splicing is of the HIV life cycle, yet little is known about the structures that control splice site selection. Splicing from donor site D4 to acceptor site A7 removes the RRE to allow expression of late phase viral proteins. Given the importance of this splicing event to controlling viral replication, the activity of splice site A7 is tightly regulated by a complex network of an intronic splicing silencer (ISS), a bipartite splicing silencer (ESS3a/b) and an exonic splicing enhancer (ESE3). RNA chemo-enzymatic probing studies have shown the isolated splice site A7 locus folds into three RNA stem loops, where the regulatory elements localize to distinct apical loops. The host hnRNP A1 protein binds SL1(ISS) and SL3(ESS3) to effectively repress splice site A7, whereas the ASF protein counteracts hnRNP A1 by binding SL2(ESE3). To gain a better understanding of the RNA structures and protein interactions that regulate A7, we have solved the high-resolution structure of the ISS stem loop. ISS folds into a 53-nt long stem-loop RNA composed of several non-canonical structural features: a UG wobble tract, a stable 2X2 internal loop, a UU bulge and a 5-nt apical loop. As a step towards understanding how hnRNP A1 gets recruited to splice site A7, we have further characterized the interaction of its UP1 domain with ISS. UP1 binds to the apical loop with high affinity and specificity. Collectively, this data provides valuable insights into developing structure based mechanisms of HIV splicing.
Keywords: Alternative splicing , HIV-1 ssA7, hnRNPA1