DNA VIRUS REPLICATION25 FEBRUARI 2020

DRH. SRUTI LISTRA ADRENALIN, M.SC.

VIRUSES

• Ukuran kecil, nonliving parasite yg tidak dpt bereplikasi di luar sel inang.

• Parasit obligat intraseluler sintesis protein.

• Terdapat informasi genetic (DNA/ RNA) yang dilapisi protein.

VIRUS DNA

• Tdk memiliki gen polymerase RNA untuk transkripsi replikasi di inti sel(terdapat polymerase RNA host).

• Virus berukuran kecil & tdk beramplop , tdk punya enzim

• As nukleat dlm virion mengandung gen untuk sitesis virus baru gen untukmengkode pembentukan komponen struktural virion dan enzim.

• Enzim hanya berfungsi saat virus dlm host (penetrasi, replikasi, pembentukan as. Nukleat).

• Host menyediakan energi, prekursor unt sintesis protein & as. Nukleat viral

… VIRUS DNA

DNA RNA

Umumnya double stranded Single stranded

Kemampuan mutase lebih rendah Kemampuan mutase tinggi

Replikasi terjadi di nucleus Replikasi di sitoplasma

Sugar deoxyribose Sugar ribose

Stabil pd kondisi alkalin Tidak stabil

Basa: adenine-thymin (AT), cytocine-guanine (CG) Adenin-uracil (AU), cytocine-guanine (CG)

Self replicating RNA disintesis dari DNA berdasarkan kebutuhan

Bertanggung jawab terhadap penyimpanan dantransfer informasi genetic

Secara langsung mengkode asam amino dan sebagaimessenger antara DNA dan ribosom untuk membuatprotein

REPLICATION

• The formation of biological viruses during the infection process in the target host cells.

• Replication cycle related to virus pathogenicity, transmission, host immune response, virus infection control.

• Strategies:

1. The virus needs to make mRNAs that can be translated into protein by the host cell translation machinery.

2. The virus needs to replicate its genome.

3. Host enzymes for mRNA synthesis and DNA replication are nuclear (except for those in mitochondrion) and so, if a virus is to avail itself of these enzymes, it needs to enter the nucleus.

• Replication cycle:

1. Attachment

2. Eclipse period (entry, uncoating, replication of component parts, virion assembly)

3. Release

DNA VIRUS REPLICATION

• Tahap awal (polymerase, replikasi, transkripsi) dan tahap akhir (kapsid, virion).

• Protein tahap awalmembuat genom virus/ mengaktifkan ekspresi gen tidakoptimal tahap laten.

• Tahap laten: Retrovirus dan Herpesvirus.

• Virus hepatitis C infeksi kronis.

ATTACHMENT

• The critical first step in the virus replication cycle.

• Requires specific interactions between components of the virus particle and components of the host cell.

• Cell-surface molecules/ receptor usage plays an important role in defining the tissue/organ specificity of a virus defines its pathogenic potential and the nature of the disease it causes.

• Different viruses may use the same receptor/entry factor.

• Viruses within a given family/ different strains of the same virus may use different receptors.

• Receptor of animal cells : proteins and glycoproteins of the plasma membrane

… ATTACHMENT

Virus Family Receptor

Adenovirus 2 Adenoviridae CAR-Ig family

Adenoviruses Adenoviridae αvβ3, αvβ5 integrins

Herpes simplex virus 1 Herpesviridae Herpes virus entry mediator A (HveA), heparan sulfateproteoglycan, others

Human cytomegalovirus Herpesviridae Heparan sulfate proteoglycan

Epstein-Barr virus Herpesviridae CD21, complement receptor 2 (CR2)

Pseudorabies virus Herpesviridae CD155—Ig family

Feline parvovirus Parvoviridae Transferrin receptor-1 (TfR-1)

Adeno-associated virus 5 Parvoviridae α(2,3)-linked sialic acid

ENTRY, UNCOATING

• Virus enters a host cell by one of two general mechanisms:

1. Direct entry across the plasma membrane.

2. Entry into the cell within a membrane-bound vesicle

• Uncoating of the virus particle occurs after the particle has entered the cell or concurrently with the cell entry process receptor can determine the entry mechanism.

• The biological stimuli that induce the entry and/or uncoating:

1. Binding to specific host cell proteins.

2. Proteolysis by host cell enzymes.

3. Exposure to acidic pH.

… ENTRY, UNCOATING

• All enveloped viruses must mediate the process of membrane fusion to enter their host cell.

• Enveloped viruses that achieve direct entry at the cell surface, fusion occurs between the virus envelope and the plasma membrane, and this process occurs under neutral pH conditions.

• Natural receptor/ligand interactions at the cell surface often initiate signaling pathways and cellular processes that lead to the internalization of the receptor/ligand complex into a membrane-bound vesicle.

• Endocytosis is the general mechanism whereby extracellular materials are internalized in membrane bound vesicles.

… ENTRY, UNCOATING

… ENTRY, UNCOATING

• Adenovirus: cell entry to the cytoplasm replication in the nucleus.

• Translocation of viral components from the cytoplasm to the nucleus is a required step in infection by almost all DNA viruses (excep Poxvirus).

• Unenveloped virus (Pynositosis) vesicles.

• Enveloped viruses (fusion) envelope + plasma membrane releases the capsidinto cell’s cytoplasma.

• Uncoating Pox enzim spesific yang disandi oleh viral DNA.

REPLIKASI, ASSEMBLY

• Replikasi genom dan ekspresi gen menentukan proses infeksi virus (akut/ kronis/ persisten/ laten).

• Virus DNA (kecuali Pox) nukleus host replikasi dan perakitan.

• Pox sitoplasmamemiliki enzim transkriptase sendiri.

• Replikasi virus DNA melibatkan mekanisme biologi sel: transkripsi mRNA dsDNA.

• Early transcription dilakukan oleh enzim transkriptase host (RNA Polymerase).

• Assembly: mengumpulkan komponen virion terjadi pembentukan strukturpartikel virus tergantung proses replikasi di dlm sel host (nukleus/ sitoplasma).

RELEASE

• 2 mekanisme:

1. Virus litik (semua virus non-enveloped): sederhana (sel host terinfeksi terbukavirus keluar).

2. Virus beramplop: perlu membrane lipid virus keluar dari sel melalui membrane (budding).

MATURATION OF ENVELOPED VIRUS

… DNA VIRUS REPLICATION

dsDNA

• Replikasi di inti sel dan tergantung padafaktor-faktor seluler (Adeno, Polyomavirus, Herpes).

• Replikasi di sitoplasma, melibatkan semuafaktor penting untuk transkripsi dan replikasidari genom, umumnya tidak bergantung pdreplication equipment host (Pox).

• Bergantung pd reverse transcription, replikasi di inti sel (Hepadna).

ssDNA

• Replikasi di inti sel intermediate double stranded sbg cetakan untuk sintesis ssDNA (Parvo).

… DNA VIRUS REPLICATION

ADENOVIRUS

• Adenoviruses code for their own DNA polymerase and DNA packaging proteins.

• Use host factors DNA replication.

• Host RNA polymerase and RNA modification systems nucleic acid synthesis needs to be in the nucleus.

REPLICATION CYCLE OF ADENOVIRUS

(1,2) virus menempel pd sel host (adanya interaksi antarareseptor permukaan virus dgn resptor sel host) virus masuk sel host melalui endositosis.

(3) Sebagian virion dibongkar di dalam endosome protein virus dilepaskanmembrane endosome terganggu virion dilepaskan ke dalam sitoplasma(uncoating)

(4) genom virus masuk ke dlm nucleus.

(5) transkripsi RNA polymerase sel host

(6) mRNA di ekspor ke sitoplasma.

(7) Translasi protein (8) masuk ke dlm nucleus mengatur transkripsi gen seluler dan virus.

(10) pre-mRNA diproses diekspor ke sitoplasma (11) translasi dan replikasi (12) diimpor ke nucleus (13) bekerjasama dgn sejumlah protein seluler.

(14) replikasi molekul virus sbg template untuk replikasiselanjutnya (15) atau transkripsi tahap akhir.

(16) mRNA akhir diproses dan diekspor ke nukleus. (17) ditranslasikan (18) protein diimpor ke dalam nukleusuntuk proses perakitan (19) pengumpulan kapsid danpembentukan virion imature dari genom virus (20, 21) virion mature terbentuk ketika protein precursor dipecaholeh protease yg memasuki inti virion virion dilepaskan

HERPESVIRUS

• Structure: virion 180-200 nm, dsDNA, envelope, icosahedral.

• Fuse directly with the cell plasma membrane partial uncoatingreplication in the nucleus.

… HERPESVIRUS

• The smallest DNA virus genome.

• Replication (uncoating, assembly) in nucleus , released by cell lysis.

• Parvoviridae can replicate autonomously ONLY in actively cycling cells (such as erythrocyte progenitors) Otherwise, co-infection with either an Adenovirus or a Herpesvirus is necessary.

• mRNA coding for the two capsid proteins (VP1 and VP2) and the non-structural protein NS1. These viral proteins are all synthesized in the cytoplasm, then imported into the nucleus.

• NS1 is essential for replication of the virus genome generating many single-stranded copies of the parvovirus genome.

PARVOVIRUS

POXVIRUS

• Structure: large virion, genome, dsDNA, enveloped, complex morphology.

• Virus bind to cell surface receptorendocytosis/ direct fusion replicate in the cytoplasm (must provide their own mRNA and DNA synthetic machinery).

POLYOMAVIRUS

• Structure: 40-60 nm, icosahedral, VP1 major capsid protein, non-enveloped, circular, dsDNA.

• Replicate in the nucleus.

• Viral capsid proteins interact with cell surface receptors and penetration via endocytosis virionsare transported to the nucleus and uncoated enter to nucleus production of viral mRNA and protein (early and late phases):

1. Early genes encode enzymes and regulatory proteins needed to start viral replication processes.

2. Late genes encode structural proteins, proteins needed for assembly of the mature virus.

… POLYOMAVIRUS

• Early and late phase of the lytic cycle.

• Early phase: recognized by host RNA polymerase transcription & RNA modification (by host enzymes) mRNA (translated in the cytoplasm).

• Late phase: DNA replication (in the nucleus) late mRNA

• Host cell provides RNA synthesis machinery, RNA modification machinery, DNA synthesis machinery, histones for packaging DNA.

• Multifunctional protein (T antigen): involved in controlling increased transcription from the late promoter and decreased transcription from early promoter, interacts with host proteins and changes the properties of the host cell playing a role in cell transformation.

• VP1, 2 and 3 mRNAs are translated in the cytoplasm, the proteins are transported to nucleus, and capsids assemble with DNA inside the capsid. Large numbers of capsids accumulate in the nucleus and form inclusion bodies. Virions are released by cell lysis.

CHARACTERISTIC OF REPLICATION OF DNA VIRUSES

REFERENCES

• Amri, I,A., Qosimah, D., Nugroho, W. 2019. Pengantar Virologi Veteriner. UB Press.

• MacLachlan, N.J., Dubovi, E.J. 2016. Fenner’s Veterinary Virology 5th Edition. Academic Press is an Imprint of Elsevier.

• Murphy, F.A., Gibbs, E.P.J., Horzinek, M.C., Studdert, M.J. 1999. Veterinary Virology 3rd Edition. Academic Press.

• http://www.microbiologybook.org/mhunt/dna1.htm

• https://www.dentalnotebook.com/human-herpesvirus-1/

TERIMA KASIH