Friedrich Hahn

Suche


A1 Interaction of the HIV-1 regulatory virus protein R (Vpr) with host cell factors

Principal investigator
Ulrich Schubert

Mentor

Functional characterization of the small regulatory HIV-1 p6 Gag protein in the viral replication cycle

The p6 protein of human immunodeficiency virus type 1 (HIV-1) represents the C-terminal domain of the HIV polyprotein Gag. Despite its small size of only 52 amino acids, p6 has many important functions in the viral life cycle.
It binds at least to two cellular budding factors Tsg101 and ALIX which are associated to the cellular ESCRT-complex, that plays a role during cytokinesis and the biogenesis of multivesicular bodies, processes that topologically resemble virus budding. Moreover, p6 is a substrate for phosphorylation, ubiquitination, and sumoylation, and mediates the incorporation of the HIV-1 accessory protein Vpr into viral particles.
Although p6 is one of the most polymorphic regions of the HIV-1 gag gene, most of its functional domains overlap with several conserved residues in p6. First, we investigated the importance of the highly conserved serine residue in position 40, which until now was not assigned to any known function of p6. We found that exchange of Ser-40 to Phe reduces virus replication in T-cell lines and in human lymphocyte tissue cultivated ex vivo. In consistency with previous data, the S40F mutation does not affect L-domain mediated virus release. Furthermore the interaction of p6 and the HIV-1 budding factor ALIX is not disturbed. However, the virus infectivity was significantly decreased when Ser-40 was mutated. It was also observed that mutation of Ser-40 selectively interferes with the cleavage between capsid (CA) and the spacer peptide SP1 resulting in an irregular morphology of the virus core and the formation of an electron dense extra core structure.
Overall, these data describe a so far unrecognized function of p6, which is mediated by Ser-40 and occurs independently of the L-domain function, but selectively affects CA maturation and virus core formation, and consequently the infectivity of released virions.

Figure:Highly conserved serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly.
A Schematic depiction of HIV-1 Gag showing matrix (MA), capsid (CA), nucleocapsid (NC) and p6. B Primary and secondary structure of p6 according to previous work. Indicated are binding sites for the cellular budding factors Tsg101 and ALIX, for the viral accessory protein Vpr as well as acceptor sites for ubiquitin (Ub) and SUMO. C Western blot of purified virus preparations of wt and S40F mutant particles revealing an accumulation of the CA-SP1 intermediate in case of the S40F mutant. D Electron microscopy images of viruses derived of wt and the S40F mutant showing representative types of viral particles. The typical morphology of wt HIV-1 virion is defined by a conical core whereas mutation of serine 40 leads to an abnormal morphology defined by a less condensed irregularly shaped core and an electron dense extra core structure. E Infectivity of wt and S40F mutant viruses after single round infections of TZM-bl indicator cells with standardized virus preparations demonstrating an about 6fold reduction for the S40F mutant.

 

Publications

Solbak, S. M., Reksten, T. R., Hahn, F., Wray, V., Henklein, P., Henklein, P., Halskau, Ø., Schubert, U., and Fossen, T. (2013). HIV-1 p6 - a structured to flexible multifunctional membrane-interacting protein. Biochimica et biophysica acta 1828, 816-823.

Solbak, S. M., Sharma, A., Bruns, K., Röder, R., Mitzner, D., Hahn, F., Niebert, R., Vedeler, A., Henklein, P., Henklein, P., Schubert, U., Wray, V., and Fossen, T. (2013). Influenza A virus protein PB1-F2 from different strains shows distinct structural signatures. Biochimica et biophysica acta 1834, 568-582.

Votteler, J., Neumann, L., Hahn, S., Hahn, F., Rauch, P., Schmidt, K., Studtrucker, N., Solbak, S. M., Fossen, T., Henklein, P., Ott, D. E., Holland, G., Bannert, N., and Schubert, U. (2011). Highly conserved serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly. Retrovirology 8, 11.

Röder, R., Bruns, K., Sharma, A., Eissmann, A., Hahn, F., Studtrucker, N., Fossen, T., Wray, V., Henklein, P. and Schubert, U. (2008). Synthesis of full length PB1-F2 influenza A virus proteins from 'Spanish flu' and 'bird flu'. J Pept Sci 14, 954-962.

 

Presentations

March 2013 The 23rd Annual Meeting of the Society for Virology. Kiel, Germany
Serine 40 of HIV-1 p6 regulates polyubiquitination and immunogenicity of Gag
Poster
     
July 2012 4th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Serine 40 in HIV-1 p6 regulates Gag ubiquitination in an L domain independent manner
Poster
     
October 2011 First International SFB 796 Conference: Mechanisms of viral host cell manipulations: from plants to humans, Bamberg, Germany
Highly conserved Serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly
Poster
     
July 2011 3rd Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Highly conserved Serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly
Poster
     
March 2011 The 21st Annual Meeting of the Society for Virology. Freiburg, Germany
Highly conserved Serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly
Poster
     

April 2010

Centennial Retrovirus Meeting. Prague, Czech Republic
Serine residues in the p6 protein of HIV-1 are phosphorylated by PKC and regulate viral core assembly
Poster