Biology ya Ma Molecular ya Mavairasi a DNA
Mavairasi a DNA ndi gulu la mavairasi omwe majini awo amapangidwa ndi deoxyribonucleic acid (DNA). Mosiyana ndi mavairasi a RNA, omwe nthawi zambiri amaberekana mofulumira komanso amakhala ndi kusintha kwakukulu, mavairasi a DNA amakhala okhazikika kwambiri majini chifukwa DNA imalimbana ndi zolakwika zoberekana. Komabe, kukhazikika sikutanthauza kuti ndi kopanda vuto: mavairasi osiyanasiyana a DNA amatha kuyambitsa matenda akuluakulu mwa anthu, nyama, ndi zomera, kuyambira matenda opatsirana kwambiri mpaka matenda obisika komanso khansa. Nkhaniyi ikukambirana mfundo zazikulu mu biology ya mavairasi a DNA, kuphatikizapo kapangidwe ka majini, njira zoberekera, mawonekedwe a majini, kuyanjana ndi maselo olandirira, komanso momwe zimakhudzira thanzi ndi sayansi ya zamoyo.
Makhalidwe ndi magulu a majini
Ma genome a kachilombo ka DNA akhoza kukhala DNA yokhala ndi zingwe ziwiri (dsDNA) kapena DNA yokhala ndi zingwe imodzi (ssDNA). Mwa anthu, ma virus ambiri ofunikira a DNA amachokera ku dsDNA, mwachitsanzo, Herpesviridae (HSV, VZV, CMV, EBV), Adenoviridae, Poxviridae, ndi Papillomaviridae (HPV). Chitsanzo chodziwika bwino cha ssDNA ndi Parvoviridae. Maonekedwe a majini amasiyananso: ena ndi olunjika (monga adenoviruses, herpesviruses), ena ndi ozungulira (monga ma papillomaviruses, polyomaviruses), ndipo ena ali ndi michira yapadera yomwe imathandiza kubwerezabwereza kapena kulongedza.
Kukula kwa majini a mavairasi a DNA kumasiyananso. Ma Parvovirus ali ndi majini ang'onoang'ono, pafupifupi 5 kb, pomwe ma poxvirus amatha kufika pa 150–300 kb. Kukula kwa majini kumagwirizana ndi kuchuluka kwa "kudziyimira pawokha" kwa kachilomboka: mavairasi akuluakulu a DNA nthawi zambiri amakhala ndi ma enzyme awoawo obwerezabwereza komanso olembedwa, pomwe majini ang'onoang'ono amadalira kwambiri makina a selo lolandira.
Kapangidwe ka tinthu tating'onoting'ono ndi kulowa m'maselo
Mavairasi a DNA nthawi zambiri amakhala ndi puloteni yotchedwa capsid yomwe imateteza majini. Ambiri ndi a icosahedral (adenoviruses, HPV), pomwe ma poxviruses ali ndi kapangidwe kovuta. Mavairasi ena a DNA omwe ali ndi mawonekedwe ofanana, monga ma herpesviruses, amapeza nembanemba kuchokera ku selo la host ndipo amanyamula ma glycoproteins kuti amangirire ku maselo olandirira maselo.
Gawo loyamba la matenda limaphatikizapo kuzindikira kwa ma receptor ndi kulowa kwa kachilombo kudzera mu endocytosis, membrane fusion, kapena njira zina. Pambuyo polowa, kachilomboka kayenera kutumiza DNA yake pamalo obwerezabwereza. Ma virus ambiri a DNA amabwerezabwereza mu nyukiliyasi, zomwe zimafuna kuti majini awo adutse m'mabowo a nyukiliya. Chosiyana kwambiri ndi ma poxvirus, omwe amabwerezabwereza ndi kulemba mu cytoplasm chifukwa amakhala ndi ma enzyme awoawo.
Njira zoberekera majini a DNA virus
Kubwerezabwereza kwa DNA ya mavairasi ndiko maziko a sayansi ya mavairasi: momwe DNA ya mavairasi imaberekedwera pogwiritsa ntchito kapena kusintha makina a m'manja.
1. Mavairasi ang'onoang'ono a DNA ndi kudalira kwa mwiniwake
Ma papillomavirus ndi ma polyomavirus amadalira kwambiri enzyme ya DNA polymerase ya selo. Chifukwa chakuti DNA polymerase ya selo imagwira ntchito makamaka panthawi ya gawo la S la kuzungulira kwa selo, mavairasi awa apanga njira "zokankhira" selo mu gawo lobwerezabwereza. Mapuloteni oyambirira monga E6 ndi E7 mu HPV amaletsa owongolera kuzungulira kwa selo (monga p53 ndi Rb), zomwe zimathandiza selo kupitiriza kugawikana ndikupereka malo abwino obwerezabwereza DNA ya kachilomboka.
2. Mavairasi akuluakulu a DNA ndi ma enzyme awoawo
Mavairasi a pox amanyamula DNA polymerase, ma enzymes opangira mRNA, ndi zinthu zolembera, zomwe zimawathandiza kuti aziberekana mu cytoplasm. Mavairasi a herpes ali pakati: mavairasi ambiri a herpes amagwiritsa ntchito polymerase yawo ya DNA ya viral koma amadalirabe zinthu zina za nyukiliya. Kuberekana kwa herpesvirus nthawi zambiri kumaphatikizapo kupanga "zigawo zobwerezabwereza" mu nyukiliya, komwe mapuloteni obwerezabwereza amasonkhana ndipo DNA ya viral imapangidwa mwamphamvu.
3. Njira zosiyanasiyana zokopera
– Kubwerezabwereza kwa Theta nthawi zambiri kumachitika mu majini ozungulira, mofanana ndi kubwerezabwereza kwa plasmid.
- Kubwerezabwereza kwa ma circle kumachitika kawirikawiri m'ma virus a herpes, zomwe zimapangitsa kuti DNA ikhale yolumikizana kwambiri ndipo imadulidwa panthawi yopaka.
- Kusamutsa kwa strand kumagwiritsidwa ntchito ndi adenovirus, mothandizidwa ndi mapuloteni otsiriza omwe amamatira kumapeto kwa DNA ngati zoyambira.
– ssDNA → dsDNA yapakati pa parvovirus: DNA yokhala ndi chingwe chimodzi imasinthidwa koyamba kukhala mawonekedwe a dsDNA ndi ma enzyme a m'maselo asanayambe kulembedwa ndi kubwerezabwereza.
Kufotokozera kwa majini: magawo "oyambirira" ndi "ochedwa"
Kufotokozera kwa majini a kachilombo ka DNA nthawi zambiri kumayendetsedwa kwakanthawi. Mwanjira ina, majini "oyambirira" amapangidwa kaye kuti akonze malo ozungulira maselo kuti aberekenso (monga mapuloteni owongolera transcriptional, mapuloteni owongolera kayendedwe ka maselo, polymerase ya DNA ya kachilombo). DNA ya kachilombo ikayamba kupangidwanso, majini "ochedwa" amapangidwa kuti apange zigawo monga mapuloteni a capsid ndi envelopu, komanso zinthu zina zosungira majini.
Lamuloli limadalira kwambiri zinthu zolimbikitsira, zowonjezera, ndi zinthu zomwe zimayambitsa mavairasi/kutulutsa ma virus. Ma virus a DNA amawongoleranso kukonza kwa RNA: njira ina yolumikizirana, polyadenylation, ndi kukhazikika kwa mRNA. Mwachitsanzo, ma adenovirus amagwira ntchito ngati zitsanzo zofunika kwambiri mu biology ya ma molekyulu chifukwa kafukufuku wa adenovirus adapangitsa kuti apezeke kuti ma mRNA alumikizane m'maselo a eukaryotic.
Kuyanjana ndi chitetezo chamthupi ndi njira zopewera matenda
Mavairasi a DNA ayenera kuthana ndi chitetezo cha mthupi monga ma interferons, njira zodziwira DNA (monga cGAS–STING), ndi mayankho a maselo a T ndi ma antibody. Mavairasi ambiri a DNA apanga mapuloteni apadera kuti aletse njirazi. Mavairasi ena a herpes amapanga mapuloteni omwe amachepetsa kuwonekera kwa antigen ya MHC, zomwe zimapangitsa maselo omwe ali ndi kachilomboka kusawoneka ndi ma lymphocyte a T omwe ali ndi poizoni. Mavairasi a Pox ali ndi mapuloteni ofanana ndi a cytokine receptor omwe amayamwa zizindikiro za chitetezo chamthupi kuti achepetse kutupa.
Kuphatikiza apo, mavairasi a DNA amatha kukhalabe obisika. Mavairasi a Herpes amadziwika kuti amayambitsa matenda obisika mu ma neuron (HSV) kapena maselo a B (EBV). Mu gawo lobisika, mawonekedwe a majini a viral amakhala ochepa, zomwe zimapangitsa kuti chitetezo cha mthupi chizivutika kuzindikira, koma kachilomboka kamasunga majini ake ndipo kamatha kuyambiranso pamene vuto la wodwalayo lafooka.
Kuphatikiza kwa majini ndi kulumikizana kwake ndi khansa
Mavairasi ena a DNA amatha kulowa mu genome ya wolandirayo kapena kusunga ma episome okhazikika. Kuphatikiza sikofunikira nthawi zonse kuti munthu abwerezenso, koma zikachitika, zimatha kukhala ndi zotsatirapo zazikulu zamoyo. Ma HPV omwe ali pachiwopsezo chachikulu (monga mitundu 16 ndi 18) amapezeka nthawi zambiri akuphatikizidwa mu khansa ya pachibelekero, zomwe zimawonjezera mawonekedwe a E6/E7, zomwe zimasokoneza p53/Rb ndikulimbikitsa kusintha kwa maselo. EBV ndi Kaposi's sarcoma-associated herpesvirus (KSHV) zimagwirizanitsidwanso ndi matenda osiyanasiyana a khansa kudzera mu kuphatikiza kwa latency, kusintha kwa ma signaling a maselo, komanso kutupa kosatha.
Kafukufuku wa mamolekyulu a mavairasi a DNA akusonyeza kuti khansa yokhudzana ndi mavairasi si chifukwa cha "kukhalapo kwa kachilomboka," koma ndi kuyanjana kovuta pakati pa majini a mavairasi, kuwongolera kayendedwe ka maselo, kukonza DNA, ndi kupsinjika kwa kusankha m'minofu yomwe yakhudzidwa.
Kupanga ndi kumasula ma virion
Pambuyo poti majini abwerezedwanso ndipo mapuloteni opangidwa amapangidwa, virion imasonkhanitsidwa. Mavairasi ambiri a DNA amasonkhanitsa capsid mu nyukiliyasi, kenako amaika DNA kudzera mu makina opakira. Mwachitsanzo, ma herpesvirus amamanga ma capsid awo mu nyukiliyasi, kenako amapeza envelopu kudzera mu njira yambiri yokhudzana ndi nembanemba ya nyukiliya ndi ma secretory organelles. Mosiyana ndi zimenezi, mavairasi osaphimbidwa monga adenoviruses nthawi zambiri amatulutsidwa maselo akamatuluka.
Gawo lokonzekera nthawi zambiri limayang'aniridwa ndi mankhwala chifukwa limakhudza kuyanjana kwa mapuloteni ndi mapuloteni enaake. Ngakhale kuti ndi lovuta kwambiri kuposa kuyang'ana ma enzyme, njira iyi ikuyamba kufufuzidwa popanga mankhwala oletsa mavairasi a m'badwo wotsatira.
Zotsatira zachipatala ndi zaukadaulo wa zamoyo
Kumvetsetsa za biology ya mavairasi a DNA kwapangitsa kuti pakhale ukadaulo ndi njira zosiyanasiyana zochiritsira. Mwachitsanzo, katemera wa HPV wochokera ku tinthu tofanana ndi kachilombo wachepetsa bwino kuchuluka kwa matenda omwe ali pachiwopsezo chachikulu. Kwa mavairasi a herpes, mankhwala monga acyclovir amasankha DNA polymerase ya kachilombo. Koma ma Adenovirus amagwiritsidwa ntchito ngati ma vector a katemera ndi majini chifukwa amapereka DNA m'maselo bwino ndipo amatha kupangidwa kuti asapatsire matenda.
Mu labotale, mavairasi a DNA amagwiranso ntchito ngati "zida" zomvetsetsa njira zoyambira za maselo a eukaryotic, kuyambira kulamulira kulembedwa kwa ma cell, kugawanika kwa ma cell, ndi kubwerezabwereza kwa DNA mpaka kuwonongeka kwa DNA ndi njira zokonzanso. Mwanjira ina, mavairasi amaonedwa osati ngati zifukwa zokha za matenda komanso ngati zitsanzo zamoyo zomwe zimathandiza kuvumbulutsa malamulo ofunikira a moyo wa maselo.
Kutseka
Sayansi ya ma virus a DNA ndi gawo lofufuza momwe ma virus ochokera ku DNA amalowera m'maselo, kutulutsa majini, kubwereza majini awo, kuthawa chitetezo chamthupi, ndikufalikira ku maselo ena. Kusiyanasiyana kwa njira zomwe zimagwiritsidwa ntchito—kuyambira kudalira makina am'manja mpaka kudzidalira kudzera mu ma enzyme awoawo—kumasonyeza kusinthasintha kodabwitsa kwa ma virus. Kumvetsetsa magawo a ma molecule awa sikuti ndikofunikira kokha pakulamulira matenda komanso kumatsegula mwayi waukulu wopanga katemera, mankhwala oletsa ma virus, ndi ukadaulo wamankhwala wozikidwa pa ma virus. Ndi kafukufuku wowonjezereka, ma virus a DNA apitiliza kupereka zenera la momwe maselo amagwirira ntchito, komanso vuto lalikulu paumoyo wa anthu wamakono.
