Adenovirus E1B protein

Adenovirus E1B protein
Identifiers
OrganismHuman adenovirus C
SymbolE1B
Entrez2652981
RefSeq (Prot)NP_040510.1
UniProtP03247
Other data
ChromosomeGenomic: 0 - 0 Mb
Search for
StructuresSwiss-model
DomainsInterPro

Adenovirus E1B protein usually refers to one of two proteins transcribed from the E1B gene of the adenovirus: a 55kDa protein and a 19kDa protein. These two proteins are needed to block apoptosis in adenovirus-infected cells. E1B proteins work to prevent apoptosis that is induced by the small adenovirus E1A protein, which stabilizes p53, a tumor suppressor.[1][2]

Functions

E1B-19k

E1B-19k blocks a p53-independent apoptosis mechanism. Without E1B-19k, degradation of both cellular and viral DNA occurs, in addition to premature host cell death during the lytic cycle, thus limiting viral replication.[3] E1B-19k mimics MCL1, which is a cellular antiapoptotic protein.[4] In infected cells, the expression of E1A results in the degradation of MCL-1, which normally binds the propaptotic protein, BAK.[4] BAK activation induces apoptosis by cooligomerizing with another proapoptotic protein, BAX. Together, BAK and BAX form pores in the mitochondrial membrane, releasing apoptogenic proteins like cytochrome c.[3][5] This and other proteins released from the mitochondria lead to activation of caspase-9 and caspase-3 and the resulting apoptotic program.[6] However, in adenovirus-infected cells, activated BAK and BAX are sequestered by E1B-19k, preventing the pathway.[3]

E1B-55k

E1B-55k blocks p53 from inhibiting cell cycling and stops it from inducing apoptosis.[7] Observations show that E1b-55k inhibits activation by p53 by binding a repression domain to it, converting it from an activator to a repressor of p53-activated genes. This stabilizes p53 and causes a large increase in p53 concentration. Additionally, p53 bound to E1B-55k has an affinity for its binding site that is ten times higher than free p53.[8] Presumably, this increased affinity and concentration of p53 turns the p53-E1B-55k complex into a powerful repressor.[9]

E1B-55k also forms a complex with E4orf6, a viral protein.[10] The E1B-55k/E4orf6 complex in infected cells assembles with other cellular proteins to form a ubiquitin ligase complex.[11] Essentially, the E1B-55k/E4orf6 complex takes over the cellular ubiquitin ligase complexes and gives them viral substrate-recognition subunits.[9] There are two known substrates for this ubiquitin ligases; p53 and the MRN complex.[11][12] The MRN complex, if not bound by the E1B-55K/E4orf6 ubiquitin ligase, will treat the ends of the viral DNA like a double-stranded DNA break and the viral DNA becomes ligated into long concatemers of randomly assorted genomes.[13]

Structural and bioinformatics studies have shown that E1B-55k, which is specific to mammalian mastadenoviruses, has evolved by exaptation from an LH3-like minor capsid protein encoded by atadenoviruses.[14]

See also

References

  1. ↑ Lowe SW, Ruley HE (April 1993). "Stabilization of the p53 tumor suppressor is induced by adenovirus 5 E1A and accompanies apoptosis". Genes & Development. 7 (4): 535–545. doi:10.1101/gad.7.4.535. PMID 8384579.
  2. ↑ White E, Cipriani R (January 1990). "Role of adenovirus E1B proteins in transformation: altered organization of intermediate filaments in transformed cells that express the 19-kilodalton protein". Molecular and Cellular Biology. 10 (1): 120–130. doi:10.1128/MCB.10.1.120. PMC 360719. PMID 2136765.
  3. 1 2 3 White E (November 2001). "Regulation of the cell cycle and apoptosis by the oncogenes of adenovirus". Oncogene. 20 (54): 7836–7846. doi:10.1038/sj.onc.1204861. PMID 11753666.
  4. 1 2 Cuconati A, Mukherjee C, Perez D, White E (December 2003). "DNA damage response and MCL-1 destruction initiate apoptosis in adenovirus-infected cells". Genes & Development. 17 (23): 2922–2932. doi:10.1101/gad.1156903. PMC 289151. PMID 14633975.
  5. ↑ Cuconati A, White E (October 2002). "Viral homologs of BCL-2: role of apoptosis in the regulation of virus infection". Genes & Development. 16 (19): 2465–2478. doi:10.1101/gad.1012702. PMID 12368257.
  6. ↑ Cory S, Huang DC, Adams JM (November 2003). "The Bcl-2 family: roles in cell survival and oncogenesis". Oncogene. 22 (53): 8590–8607. doi:10.1038/sj.onc.1207102. PMID 14634621.
  7. ↑ Debbas M, White E (April 1993). "Wild-type p53 mediates apoptosis by E1A, which is inhibited by E1B". Genes & Development. 7 (4): 546–554. doi:10.1101/gad.7.4.546. PMID 8384580.
  8. ↑ Martin ME, Berk AJ (April 1998). "Adenovirus E1B 55K represses p53 activation in vitro". Journal of Virology. 72 (4): 3146–3154. doi:10.1128/JVI.72.4.3146-3154.1998. PMC 109770. PMID 9525640.
  9. 1 2 Berk AJ (November 2005). "Recent lessons in gene expression, cell cycle control, and cell biology from adenovirus". Oncogene. 24 (52): 7673–7685. doi:10.1038/sj.onc.1209040. PMID 16299528.
  10. ↑ Sarnow P, Hearing P, Anderson CW, Halbert DN, Shenk T, Levine AJ (March 1984). "Adenovirus early region 1B 58,000-dalton tumor antigen is physically associated with an early region 4 25,000-dalton protein in productively infected cells". Journal of Virology. 49 (3): 692–700. doi:10.1128/JVI.49.3.692-700.1984. PMC 255526. PMID 6699935.
  11. 1 2 Querido E, Blanchette P, Yan Q, Kamura T, Morrison M, Boivin D, et al. (December 2001). "Degradation of p53 by adenovirus E4orf6 and E1B55K proteins occurs via a novel mechanism involving a Cullin-containing complex". Genes & Development. 15 (23): 3104–3117. doi:10.1101/gad.926401. PMC 312842. PMID 11731475.
  12. ↑ Stracker TH, Carson CT, Weitzman MD (July 2002). "Adenovirus oncoproteins inactivate the Mre11-Rad50-NBS1 DNA repair complex". Nature. 418 (6895): 348–352. Bibcode:2002Natur.418..348S. doi:10.1038/nature00863. PMID 12124628. S2CID 4413110.
  13. ↑ Weiden MD, Ginsberg HS (January 1994). "Deletion of the E4 region of the genome produces adenovirus DNA concatemers". Proceedings of the National Academy of Sciences of the United States of America. 91 (1): 153–157. Bibcode:1994PNAS...91..153W. doi:10.1073/pnas.91.1.153. PMC 42904. PMID 8278357.
  14. ↑ Marabini R, Condezo GN, Krupovic M, Menéndez-Conejero R, Gómez-Blanco J, San Martín C (March 2021). "Near-atomic structure of an atadenovirus reveals a conserved capsid-binding motif and intergenera variations in cementing proteins". Science Advances. 7 (14) eabe6008. Bibcode:2021SciA....7.6008M. doi:10.1126/sciadv.abe6008. PMC 8011978. PMID 33789897.
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