CccDNA

cccDNA (covalently closed circular DNA) is a special DNA structure that arises during the propagation of some viruses in the cell nucleus and may remain permanently there. It is a double-stranded DNA that originates in a linear form that is ligated by means of DNA ligase to a covalently closed ring. In most cases, transcription of viral DNA can occur from the circular form only. The cccDNA of viruses is also known as episomal DNA or occasionally as a minichromosome.

cccDNA was first described in bacteriophages, but it was also found in some cell cultures where an infection of DNA viruses (Polyomaviridae) was detected.[1][2] cccDNA is typical of Caulimoviridae and Hepadnaviridae, including the hepatitis B virus (HBV). cccDNA in HBV is formed by conversion of capsid-associated relaxed circular DNA (rcDNA).[3] Following hepatitis B infections, cccDNA can remain following clinical treatment in liver cells and can rarely reactivate. The relative quantity of cccDNA present is an indicator for HBV treatment.[4]

  1. ^ Mosevitskaia TV, Pavel'chuk EB, Tomilin NV (1976). "[Substrate of a UV-induced repair system providing for W-reactivation of lambda phage]". Genetika (in Russian). 12 (8): 131–8. PMID 1001892.
  2. ^ Kunisada, T.; H. Yamagishi (November 1984). "Sequence repetition and genomic distribution of small polydisperse circular DNA purified from HeLa cells". Gene. 31 (1–3): 213–223. doi:10.1016/0378-1119(84)90212-9. PMID 6098526.
  3. ^ Guo H.; D. Jiang; T. Zhou; A. Cuconati; T.M. Block; J.T. Guo (November 2007). "Characterization of the intracellular deproteinized relaxed circular DNA of hepatitis B virus: an intermediate of covalently closed circular DNA formation". J Virol. 81 (22): 12472–12484. doi:10.1128/JVI.01123-07. PMC 2169032. PMID 17804499.
  4. ^ Bourne, E.J.; Dienstag, J.L.; Lopez, V.A.; et al. (January 2007). "Quantitative analysis of HBV cccDNA from clinical specimens: correlation with clinical and virological response during antiviral therapy". Journal of Viral Hepatitis. 14 (1): 56–63. doi:10.1111/j.1365-2893.2006.00775.x. PMID 17212645. S2CID 21563920.