The replication cycle of hepatitis B virus

Abstract

Liver unit, IFI Institute for InterdisciplinaryMedicine, Asklepios Clinics St. Georg, Hamburg, Germany(1) Reversible and non-cell-type specific attachment to cell-associated heparan sulfate proteoglycans.(2) Specific and probably irreversible binding to an unknownhepatocyte-specific preS1-receptor. This step presumablyrequires activation of the virus resulting in exposure ofthe myristoylated N-terminus of the L-protein [1].(3) Two different entry pathways have been proposed: (3A)endocytosis followed by release of nucleocapsids fromendocytic vesicles; (3B) fusion of the viral envelope atthe plasma membrane.(4) Cytoplasmic release of the viral nucleocapsid containingthe relaxed circular partially double stranded DNA (rcDNA)with its covalently linked polymerase.(5) Transport of the nucleocapsid along microtubules. Accu-mulation of the capsids at the nuclear envelope facilitatesinteractions with adaptor proteins of the nuclear porecomplex.(6) Possible trapping of the nucleocapsid in the nuclear basketand release of rcDNA into the nucleoplasm. The mecha-nisms determining the breakdown of the capsid and therelease of the viral DNA genome are unsolved [2].(7) ‘‘Repair” of the incoming rcDNA: Completion of the plusstrand of the rcDNA by the viral polymerase. Removal ofthe polymerase from the 5