The chromosomal protein HMG-D binds to the TAR and RBE RNA of HIV-1

The high mobility group protein HMG-D is known to bind preferentially to DN A of irregular structures with little or no sequence specificity, Upon bind ing to DNA, this HMG-box protein widens the minor groove of the double heli x and induces a significant bending of the helix, We show here that HMG-D c an strongly bind to double-stranded RNA, Electrophoretic mobility shift ass ays show that HMG-D100 interacts with the transactivation response region ( TAR) RNA from HIV-1. Strong interaction with a high affinity Rev protein bi nding element (RBE) RNA was also characterized. Gel shift experiments perfo rmed with several TAR RNA constructs lacking the lateral pyrimidine bulge o r with modified apical loop regions indicate that the protein does not reco gnize the single-strand domains of the RNA but apparently interacts directl y with the double-stranded stem regions. No protein-RNA complexes could be detected when using single-stranded oligoribonucleotides. HMG-D protein cou ld bind to the wide minor groove of the A-form TAR RNA. The comparison of t he amino acid sequence of HMG-D with that of known RNA binding proteins sug gests that the interaction of the protein with a double-stranded RNA implic ates the basic region of HMG-D as well as its HMG-box domain. From the in v itro data reported here, we propose a novel functional role for proteins of the HMG-1 family. The results suggest that architectural HMG proteins can be recruited by double-stranded RNA for the development of HIV-1 in the hos t cell. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.