Niaj hnub nimno biology amazes nrog lub uniqueness thiab scale ntawm nws discoveries. Niaj hnub no, qhov kev tshawb fawb no kawm feem ntau ntawm cov txheej txheem uas zais ntawm peb lub qhov muag. Qhov no yog qhov zoo tshaj plaws rau molecular biology - ib qho ntawm cov chaw cog lus uas yuav pab kom tshem tawm cov kev paub tsis meej tshaj plaws ntawm kev muaj sia nyob.
Dab tsi yog kev hloov pauv rov qab
Rov qab sau dua (RT luv luv) yog cov txheej txheem tshwj xeeb ntawm cov kab mob RNA feem ntau. Nws lub ntsiab feature yog synthesis ntawm ob-stranded DNA molecule raws li tus tub txib RNA.
OT tsis yog tus yam ntxwv ntawm cov kab mob lossis cov kab mob eukaryotic. Lub ntsiab enzyme, reversetase, plays lub luag hauj lwm tseem ceeb nyob rau hauv lub synthesis ntawm ob-stranded DNA.
Discovery keeb kwm
Lub tswv yim uas ribonucleic acid molecule tuaj yeem dhau los ua qauv rau DNA synthesis tau suav tias yog qhov tsis txaus ntseeg txog xyoo 1970. Ces B altimore thiab Temin, ua hauj lwm sib cais los ntawm ib leeg, yuav luag ib txhij nrhiav tau ib tug tshiab enzyme. Lawv hu nws RNA-dependent-DNA polymerase, lossis thim rov qab transcriptase.
Qhov kev tshawb pom ntawm cov enzyme no tsis muaj xwm txheej tau lees paub tias muaj cov kab mobmuaj peev xwm thim rov qab. Ob tus kws tshawb fawb tau txais Nobel nqi zog hauv xyoo 1975. Tom qab qee lub sijhawm, Engelhardt tau thov lwm lub npe rau thim rov qab transcriptase - revertase.
Vim li cas OT contradicts lub hauv paus dogma ntawm molecular biology
Lub Central Dogma yog lub tswv yim ntawm cov protein synthesis nyob rau hauv txhua lub cell. Cov tswv yim zoo li no yog tsim los ntawm peb yam: DNA, RNA thiab protein.
Raws li lub hauv paus dogma, RNA tuaj yeem raug tsim tshwj xeeb rau ntawm DNA qauv, thiab tsuas yog tom qab ntawd RNA koom nrog hauv kev tsim cov qauv tseem ceeb ntawm cov protein.
Qhov dogma no tau raug lees paub hauv zej zog kev tshawb fawb ua ntej qhov kev tshawb pom ntawm kev hloov pauv rov qab. Tsis yog qhov xav tsis thoob, lub tswv yim ntawm kev rov qab synthesis ntawm DNA los ntawm RNA tau ntev lawm tsis lees paub los ntawm cov kws tshawb fawb. Tsuas yog xyoo 1970, nrog rau qhov kev tshawb pom ntawm qhov rov qab los, yog qhov kawg ntawm qhov teeb meem no, uas tau tshwm sim hauv lub tswv yim ntawm cov protein synthesis.
Revertase ntawm avian retroviruses
Cov txheej txheem ntawm kev hloov pauv rov qab tsis tiav yog tias tsis muaj kev koom tes ntawm RNA-dependent-DNA polymerase. Revertase ntawm avian retrovirus tau kawm txog qhov siab tshaj plaws rau hnub tim.
Tsuas muaj li ntawm 40 lub molecules ntawm cov protein no tuaj yeem pom nyob rau hauv ib qho virion ntawm tsev neeg cov kab mob no. Cov protein muaj ob lub subunits uas sib npaug thiab ua peb lub luag haujlwm tseem ceeb ntawm kev thim rov qab:
1) Synthesis ntawm DNA molecule ob leeg ntawm ib leeg-stranded/ob-stranded RNA template thiab raws li deoxyribonucleic acids.
2) RNase H ua kom, lub luag haujlwm tseem ceeb ntawm kev ua haujlwmcleavage ntawm RNA molecule hauv RNA-DNA complex.
3) Kev puas tsuaj ntawm ntu ntawm DNA molecules rau kev ntxig rau hauv eukaryotic genome.
Mechanism OT
Cov kauj ruam rov qab tuaj yeem sib txawv nyob ntawm tsev neeg tus kab mob, piv txwv li. ntawm hom ntawm lawv cov nucleic acids.
Cia peb pib xav txog cov kab mob uas siv rov qab los. Ntawm no cov txheej txheem OT tau muab faib ua 3 kauj ruam:
1) Kev sib xyaw ntawm "-" RNA strand ntawm tus qauv "+" ntawm RNA strand.
2) Kev puas tsuaj ntawm "+" strand ntawm RNA hauv RNA-DNA complex siv cov enzyme RNase H.
3) Kev sib xyaw ntawm ob txoj hlua DNA molecule ntawm tus qauv "-" ntawm RNA saw.
Txoj kev no ntawm virion reproduction yog ib yam rau qee tus kab mob oncogenic thiab tib neeg immunodeficiency virus (HIV).
Nws tsim nyog sau cia tias rau kev sib txuas ntawm ib qho nucleic acid ntawm RNA template, xav tau ib lub noob los yog primer. Ib tug primer yog ib tug luv luv sequence ntawm nucleotides uas yog complementary mus rau lub 3 'kawg ntawm ib tug RNA molecule (template) thiab plays ib tug tseem ceeb luag hauj lwm nyob rau hauv pib synthesis.
Thaum npaj txhij-ua ob-stranded DNA molecules ntawm viral keeb kwm yog kev koom ua ke rau hauv eukaryotic genome, ib txwm mechanism ntawm virion protein synthesis pib. Raws li qhov tshwm sim, lub xov tooj ntawm tes "ntim" los ntawm tus kab mob no dhau los ua lub chaw tsim khoom virion, qhov uas tsim nyog cov protein thiab RNA molecules tau tsim los ntawm ntau qhov ntau.
Lwm txoj kev ntawm kev thim rov qab yog ua raws li kev ua ntawm RNA synthetase. Cov protein no ua haujlwm hauv paramyxoviruses, rhabdoviruses, picornoviruses. Hauv qhov no, tsis muaj theem peb ntawm OT - kev tsimob-stranded DNA, thiab hloov, ib tug "+" RNA saw yog synthesized ntawm tus qauv ntawm tus kab mob "-" RNA saw thiab vice versa.
Kev rov ua dua ntawm cov voj voog no ua rau ob qho tib si rov ua dua ntawm tus kab mob genome thiab tsim mRNA muaj peev xwm ntawm cov protein synthesis nyob rau hauv cov xwm txheej ntawm cov kab mob eukaryotic cell.
Kev lom neeg tseem ceeb ntawm kev hloov pauv rov qab
Cov txheej txheem OT yog qhov tseem ceeb tshaj plaws hauv lub neej ntawm ntau tus kab mob (feem ntau cov kab mob retroviruses xws li HIV). RNA ntawm ib tug virion uas tawm tsam eukaryotic cell dhau los ua qauv rau kev sib txuas ntawm thawj DNA strand, uas nws tsis yooj yim los ua kom tiav cov kab thib ob.
Qhov tau txais ob-kab DNA ntawm tus kab mob no tau koom ua ke rau hauv eukaryotic genome, uas ua rau kev ua kom cov txheej txheem ntawm virion protein synthesis thiab pom ntau ntawm nws cov ntawv luam hauv cov kab mob. Nov yog lub hom phiaj tseem ceeb ntawm Revertase thiab OT feem ntau rau tus kab mob.
Rov qab sau dua tuaj yeem tshwm sim hauv eukaryotes nyob rau hauv cov ntsiab lus ntawm retrotransposons - cov noob caj noob ces uas tuaj yeem thauj tus kheej ntawm ib feem ntawm cov genome mus rau lwm qhov. Cov ntsiab lus zoo li no, raws li cov kws tshawb fawb, ua rau muaj kev hloov pauv ntawm cov kab mob nyob.
Retrotransposon yog qhov ncab ntawm eukaryotic DNA uas code rau ntau cov proteins. Ib tug ntawm lawv, reversetase, yog ncaj qha koom nyob rau hauv lub delocalization ntawm xws retrotransporozone.
Kev siv OT hauv kev tshawb fawb
Txij li lub sijhawm thaum rov qab thim rov qab raug cais tawm hauv nws daim ntawv ntshiab, cov txheej txheem ntawm kev thim rov qab tau txais los ntawm biologists. Txoj kev kawm ntawm OT mechanism tseem pab nyeem cov kab ke ntawm tib neeg cov proteins tseem ceeb tshaj plaws.
Qhov tseeb yog tias cov genome ntawm eukaryotes, suav nrog peb, muaj cov cheeb tsam tsis muaj ntaub ntawv hu ua introns. Thaum cov nucleotide ib ntus tau nyeem los ntawm cov DNA zoo li no thiab ib leeg-stranded RNA raug tsim, tom kawg poob introns thiab cov lej tshwj xeeb rau cov protein. Yog hais tias DNA yog synthesized siv reversetase ntawm ib tug RNA template, ces nws yog ib qho yooj yim mus ua raws nws thiab nrhiav kom paub qhov kev txiav txim ntawm nucleotides.
Nucleic acid uas tau tsim los ntawm kev rov qab transcriptase hu ua cDNA. Nws feem ntau yog siv rau hauv cov tshuaj tiv thaiv kab mob polymerase (PCR) txhawm rau txhawm rau nce tus lej luam ntawm cov txiaj ntsig cDNA. Txoj kev no tsis yog siv hauv kev tshawb fawb nkaus xwb, tab sis kuj tseem nyob hauv cov tshuaj: cov kws pab kuaj mob txiav txim siab qhov zoo sib xws ntawm DNA nrog cov genomes ntawm ntau yam kab mob los yog kab mob los ntawm ib lub tsev qiv ntawv. Lub synthesis ntawm vectors thiab lawv cov kev taw qhia rau hauv cov kab mob yog ib qho ntawm cov kev cog lus ntawm biology. Yog tias RT siv los tsim cov DNA ntawm tib neeg thiab lwm yam kab mob uas tsis muaj introns, cov molecules no tuaj yeem yooj yim nkag mus rau hauv cov kab mob genome. Yog li tom kawg dhau los ua cov chaw tsim khoom tsim khoom tsim nyog rau tus neeg (piv txwv li, enzymes).
