Analyse du transport intracytoplasmique de la capside du virus de l’hépatite B : analyse des interactions entre les capsides du VHB et les chaînes du complexe de la dynéine

摘要

Hepatitis B virus (HBV) needs the nuclear transcription machinery for replication. The virus thus depends on the transport of its genome from the cell periphery to the nuclear envelope. In general this retrograde intracytoplasmic trafficking is facilitated along Mt (MT) using motor protein complexes of the dynein family. As we showed earlier HBV capsid transport also depends upon intact MT in order to allow their arrival at the nuclear pores, which in turn is required for genome liberation from the capsid.In the analysis we used virus-derived HBV capsids obtained from the supernatant of HepG2.2.15, which contain the mature partially double-stranded DNA genome (mature capsids) and capsids expressed in E. coli. The latter were applied in two forms: as unspecific E. coli RNA- containing capsids and as empty capsids. Upon microinjection into Xenopus laevis oocytes we observed that mature and empty capsids were translocated to the nuclear pores with a similar kinetic. RNA-containing capsids failed to arrive at the pores implying that transport of the two other capsid types was active. Active translocation was confirmed by pre-injecting anti tubulin antibodies which interfere with MT-mediated translocation.In vitro reconstitution assays confirmed the specific attachment of mature and empty capsids to MTs and showed the need of further cytosolic proteins. Using pull-down and co-sedimentation experiments we identified one dynein light chain (DYNLL1, member of the Lc8 family) as interaction partner of the capsids. Injecting an excess of recombinant DYNLL1 with empty capsids into Xenopus laevis oocytes inhibited capsid transport to the nuclear pores indicating that DYNLL1 was only functional interaction partner implied in active transport.DNYLL2 did not interact with the capsids although differing from DYNLL1 by just six amino acids. Site directed mutagenesis of DYNLL1 revealed that two amino acids were critical for a direct interaction with the capsids. Both localized at the exterior of the DYNLL1 dimer and not in the groove of DYNLL1, which interacts with the dynein intermediate chain. Accordingly we could reconstitute a complex consisting of empty capsids, DYNLL1 and dynein intermediate chain as it should be in the in vivo situation.