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Retroviruses and Hepatitis B Virus. Rous Sarcoma Virus. Hepatitis B Virus. HBV Genome. Genome Organization. 4 classes of mRNA in green : 0.9kb, 2.1kb, 2.4kb, 3.5kb. Pregenome RNA blue. Outline of Genome Replication. The pregenome RNA acts as template for DNA synthesis .
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4 classes of mRNA in green : 0.9kb, 2.1kb, 2.4kb, 3.5kb Pregenome RNA blue
Outline of Genome Replication • The pregenome RNA acts as template for DNA synthesis. • Initially a 4-nucleotide (−) DNA is synthesized then it is transferred to a complementary sequence in DR1 near the 3 end of the pregenome. • DNA synthesis continues to the 5 end of the pregenometemplate. The RNase H activity of the P protein degrades the pregenome RNA from the RNADNA duplex. • All the RNA is removed except for a remnant of 15–18 bases including the cap. The –OH group at the 3 end of the RNA remnant acts as the primer for the synthesis of (+) DNA. • During (+) DNA synthesis a nucleocapsidcan either migrate to the nucleus to increase the pool of cccDNAor it can undergo a maturation event that enables it to bud through a membrane containing virus envelopeproteins • DNA synthesisceases on budding, as the nucleocapsid is cut off from the pool of nucleotides in the cytoplasm. • This explains why the (+) DNA in the virion is incomplete?