第八章基因表達(dá)調(diào)控學(xué)習(xí)教案

1、會(huì)計(jì)學(xué)1第八章基因表達(dá)第八章基因表達(dá)(biod)調(diào)控調(diào)控第一頁(yè)，共62頁(yè)。proteintranscriptiontranslationDNARNA基因表達(dá)就是(jish)基因轉(zhuǎn)錄及翻譯過(guò)程。第1頁(yè)/共62頁(yè)第二頁(yè)，共62頁(yè)。第2頁(yè)/共62頁(yè)第三頁(yè)，共62頁(yè)。(biod)一類基因。一類基因。v誘導(dǎo)和阻遏表達(dá)誘導(dǎo)和阻遏表達(dá)(biod)（ induction and repression ）：）：受環(huán)境因素影響而呈現(xiàn)出基因受環(huán)境因素影響而呈現(xiàn)出基因表達(dá)表達(dá)(biod)升高（誘導(dǎo)）或升高（誘導(dǎo)）或降低（阻遏）的現(xiàn)象。降低（阻遏）的現(xiàn)象。第3頁(yè)/共62頁(yè)第四頁(yè)，共62頁(yè)。Programming Gen

2、e Expression. Complex biological processes often involve coordinated control of the expression of many genes. The maturation of a tadpole into a frog is largely controlled by thyroid hormone. This hormone regulates gene expression by binding to a protein, the thyroid hormone receptor, shown at the r

3、ight. In response to hormone binding, this protein binds to specific DNA sites in the genome and modulates the expression of nearby genes. 第4頁(yè)/共62頁(yè)第五頁(yè)，共62頁(yè)。Diagram of the human globin family of genes on chromosome第5頁(yè)/共62頁(yè)第六頁(yè)，共62頁(yè)。1Procarboxypeptidase A17.6Albumin3.52Pancreatic trypsinogen 25.5Apolip

4、oprotein A-I2.83Chymotrypsinogen4.4Apolipoprotein C-I2.54Pancreatic trypsin 13.7Apolipoprotein C-III2.15Elastase IIIB2.4ATPase 6/81.56Protease E1.9Cytochrome oxidase 31.17Pancreatic lipase1.9Cytochrome oxidase 21.18Procarboxypeptidase B1.7a a-1-Antitrypsin1.09Pancreatic amylase1.7Cytochrome oxidase

5、10.910Bile salt-stimulated lipase1.4Apolipoprotein E0.9RankPancreas%Liver%Highly expressed protein-encoding genes of the pancreas and liver (as percentage of total mRNA pool)第6頁(yè)/共62頁(yè)第七頁(yè)，共62頁(yè)。轉(zhuǎn)錄(zhun l)翻譯(fny)v 基因表達(dá)(biod)的多級(jí)調(diào)控D N AR N APROTEIN第7頁(yè)/共62頁(yè)第八頁(yè)，共62頁(yè)。第8頁(yè)/共62頁(yè)第九頁(yè)，共62頁(yè)。 P O A B C調(diào)控(dio kn)序列（區(qū)

6、） 編碼序列（區(qū)）第9頁(yè)/共62頁(yè)第十頁(yè)，共62頁(yè)。v 操縱序列 (operator,O)：是阻遏蛋白(dnbi)結(jié)合位點(diǎn)，與啟動(dòng)子序列毗鄰，常交叉、重疊。介導(dǎo)負(fù)性調(diào)節(jié)v 激活蛋白(dnbi)結(jié)合序列-介導(dǎo)正性調(diào)節(jié)第10頁(yè)/共62頁(yè)第十一頁(yè)，共62頁(yè)。 間隔(jin g) -35區(qū) 間隔(jin g) RNA起始(q sh)TTGACA N17TTAACT N7 ATTTACA N16TATGAT N7 ATTTACA N17TATGTT N6 ATTGATA N16TATAAT N7 ACTGACG N18TACTGT N6 A -10區(qū)+1trptRNATyrlacRec Aara B A

7、 D TTGACATATAAT共有序列第11頁(yè)/共62頁(yè)第十二頁(yè)，共62頁(yè)。2、真核生物基因表達(dá)調(diào)控序列順式作用元件（cis-acting element）: 影響自身基因表達(dá)活性的序列，位于(wiy)基因的兩側(cè)或中間： 啟動(dòng)子（promoter） 增強(qiáng)子 (enhancer) 沉默子 (silencer) 第12頁(yè)/共62頁(yè)第十三頁(yè)，共62頁(yè)。BARNA聚合酶BADNADNA轉(zhuǎn)錄(zhun l)起始點(diǎn)mRNAmRNA圖 14-2 順式作用元件(yunjin)概念轉(zhuǎn)錄(zhun l)起始點(diǎn)RNA聚合酶第13頁(yè)/共62頁(yè)第十四頁(yè)，共62頁(yè)。第14頁(yè)/共62頁(yè)第十五頁(yè)，共62頁(yè)。蛋白質(zhì)mRNAPA

8、DNAPB轉(zhuǎn)錄(zhun l)起始點(diǎn)mRNA順式調(diào)節(jié)(tioji)蛋白質(zhì)圖 14-3 反式與順式作用(zuyng)蛋白反式調(diào)節(jié)BA第15頁(yè)/共62頁(yè)第十六頁(yè)，共62頁(yè)。（四）RNA聚合酶活性： 啟動(dòng)子序列影響(yngxing)其與RNA聚合酶的親合力。 調(diào)節(jié)蛋白影響(yngxing)RNA聚合酶的活性。 第16頁(yè)/共62頁(yè)第十七頁(yè)，共62頁(yè)。第17頁(yè)/共62頁(yè)第十八頁(yè)，共62頁(yè)。第18頁(yè)/共62頁(yè)第十九頁(yè)，共62頁(yè)。（一）結(jié)構(gòu)組成： 調(diào)控區(qū)：Plac、O、CAP結(jié)合(jih)位點(diǎn)和 編碼區(qū)：三個(gè)結(jié)構(gòu)基因（Z、Y、A） 操縱元外有調(diào)節(jié)基因（lacI）編碼阻遏蛋白一、乳糖(r tn)操縱元（lac

9、tose operon）第19頁(yè)/共62頁(yè)第二十頁(yè)，共62頁(yè)。圖162乳糖(r tn)操縱子的結(jié)構(gòu)第20頁(yè)/共62頁(yè)第二十一頁(yè)，共62頁(yè)。（二）調(diào)節(jié)方式： 阻遏蛋白(dnbi)的負(fù)性調(diào)節(jié) CAP的正性調(diào)節(jié) 協(xié)調(diào)調(diào)節(jié)第21頁(yè)/共62頁(yè)第二十二頁(yè)，共62頁(yè)。IPTG(乳糖(r tn)類似物)阻遏蛋白(dnbi)的負(fù)性調(diào)節(jié)第22頁(yè)/共62頁(yè)第二十三頁(yè)，共62頁(yè)。CAP的正性調(diào)節(jié)(tioji)CAP腺苷酸環(huán)化酶催化ATP生成(shn chn)cAMP; cAMP磷二酯酶水解cAMP產(chǎn)生5-AMP 第23頁(yè)/共62頁(yè)第二十四頁(yè)，共62頁(yè)。圖163乳糖操縱子對(duì)基因(jyn)表達(dá)的調(diào)節(jié)第24頁(yè)/共62頁(yè)第二

10、十五頁(yè)，共62頁(yè)。協(xié)調(diào)(xitio)調(diào)節(jié)v 當(dāng)阻遏蛋白封閉(fngb)轉(zhuǎn)錄時(shí)，CAP對(duì)該系統(tǒng)不能發(fā)揮作用；v 沒(méi)有CAP時(shí)，即使阻遏蛋白從operator上解離仍無(wú)明顯的轉(zhuǎn)錄活性；v 若有葡萄糖和乳糖時(shí)，細(xì)菌優(yōu)先利用葡萄糖-分解代謝阻遏（catabolic repression）第25頁(yè)/共62頁(yè)第二十六頁(yè)，共62頁(yè)。2CAP cAMPCAP位點(diǎn)低乳糖(r tn)阻遏(z )蛋白操縱(cozng)序列高乳糖RNA聚合酶mRNA 5圖 14-5 CAP,阻遏蛋白，cAMP和誘導(dǎo)劑對(duì)lac操縱子的調(diào)節(jié) 1.當(dāng)葡萄糖濃度低，cAMP濃度高時(shí) 2.當(dāng)葡萄糖濃度高，cAMP濃度低時(shí) 啟動(dòng)序列啟動(dòng)序列啟動(dòng)

11、序列啟動(dòng)序列1第26頁(yè)/共62頁(yè)第二十七頁(yè)，共62頁(yè)。阻遏蛋白的負(fù)調(diào)控；阻遏蛋白的負(fù)調(diào)控；輔阻遏物輔阻遏物 ( 色氨酸色氨酸 ) +輔阻遏蛋白輔阻遏蛋白=阻遏蛋白阻遏蛋白衰減子衰減子 （trp a）機(jī)制）機(jī)制第27頁(yè)/共62頁(yè)第二十八頁(yè)，共62頁(yè)。v阻遏(z )蛋白的負(fù)調(diào)控第28頁(yè)/共62頁(yè)第二十九頁(yè)，共62頁(yè)。 色氨酸操縱子的結(jié)構(gòu)(jigu)第29頁(yè)/共62頁(yè)第三十頁(yè)，共62頁(yè)。 色氨酸操縱子對(duì)轉(zhuǎn)錄的調(diào)控(dio kn)機(jī)制第30頁(yè)/共62頁(yè)第三十一頁(yè)，共62頁(yè)。圖166 噬菌體的開(kāi)關(guān)(kigun)事件操縱基因的結(jié)構(gòu)第31頁(yè)/共62頁(yè)第三十二頁(yè)，共62頁(yè)。衰減子（attenuator）：提前

12、終止轉(zhuǎn)錄，調(diào)節(jié)基因表達(dá)的DNA序列。位于轉(zhuǎn)錄起始點(diǎn)前，存在前導(dǎo)序列（162nt）中，當(dāng)trp濃度很高時(shí)， 在與轉(zhuǎn)錄偶聯(lián)的翻譯過(guò)程中，在mRNA分子上形成一個(gè)不依賴(yli)因子的終止結(jié)構(gòu)。v 轉(zhuǎn)錄衰減(shui jin)機(jī)制1234第32頁(yè)/共62頁(yè)第三十三頁(yè)，共62頁(yè)。轉(zhuǎn)錄衰減(shui jin)機(jī)制第33頁(yè)/共62頁(yè)第三十四頁(yè)，共62頁(yè)。第34頁(yè)/共62頁(yè)第三十五頁(yè)，共62頁(yè)。第35頁(yè)/共62頁(yè)第三十六頁(yè)，共62頁(yè)。第36頁(yè)/共62頁(yè)第三十七頁(yè)，共62頁(yè)。第37頁(yè)/共62頁(yè)第三十八頁(yè)，共62頁(yè)。第38頁(yè)/共62頁(yè)第三十九頁(yè)，共62頁(yè)。（一）順式作用元件 啟動(dòng)子：含有一組轉(zhuǎn)錄控制組件（mod

13、ule） 轉(zhuǎn)錄起始點(diǎn) TATA 盒:位于-25-35bp處，是TFIID結(jié)合位點(diǎn)，控制轉(zhuǎn)錄的準(zhǔn)確性和頻率 CAAT盒 GC 盒 增強(qiáng)子（enhancer） ： 增強(qiáng)啟動(dòng)子轉(zhuǎn)錄活性的DNA序列。含有若干功能組件增強(qiáng)體（enhanson）是TF結(jié)合的核心序列 位于啟動(dòng)子內(nèi)、或交錯(cuò)、或相鄰、或其它部位(bwi) 遠(yuǎn)距離起作用 ， 專一性不強(qiáng) ， 無(wú)方向性 沉默子（silencer）負(fù)性調(diào)控元件，當(dāng)結(jié)合特異調(diào)控蛋白因子時(shí)，對(duì)基因轉(zhuǎn)錄起阻遏作用。 第39頁(yè)/共62頁(yè)第四十頁(yè)，共62頁(yè)。General pattern of cis-acting control elements that regulate

14、 gene expression in yeast and multicellular organisms (invertebrates, vertebrates, and plants). (a) Genes of multicellular organisms contain both promoter-proximal elements and enhancers as well as a TATA box or other promoter element. The latter positions RNA polymerase II to initiate transcription

15、 at the start site and influences the rate of transcription. Enhancers may be either upstream or downstream and as far away as 50 kb from the transcription start site. In some cases, promoter-proximal elements occur downstream from the start site as well. (b) Most yeast genes contain only one regula

16、tory region, called an upstream activating sequence (UAS), and a TATA box, which is 90 base pairs upstream from the start site. 第40頁(yè)/共62頁(yè)第四十一頁(yè)，共62頁(yè)。Nucleotide sequence of the human -globin gene 第41頁(yè)/共62頁(yè)第四十二頁(yè)，共62頁(yè)。Nucleotide sequence of the human -globin gene 第42頁(yè)/共62頁(yè)第四十三頁(yè)，共62頁(yè)。第43頁(yè)/共62頁(yè)第四十四頁(yè)，共62頁(yè)。

17、2. 轉(zhuǎn)錄調(diào)節(jié)因子結(jié)構(gòu) DNA結(jié)合域(DNA binding domain): 鋅指結(jié)構(gòu) (zinc finger) 堿性亮氨酸拉鏈（basic leucine zipper,bZIP） 堿性螺旋(luxun)-環(huán)-螺旋(luxun)（basic helix-loop-helix,bHLH） 轉(zhuǎn)錄激活域(activation domain)： 酸性激活域(acidic activation domain) 谷氨酰胺富含域(glutamine-rich domain) 脯氨酸富含域(proline-rich domain) 二聚化結(jié)構(gòu)域(dimerization domain)： ZIP 、HL

18、H 第44頁(yè)/共62頁(yè)第四十五頁(yè)，共62頁(yè)。圖167鋅指結(jié)構(gòu)(jigu)第45頁(yè)/共62頁(yè)第四十六頁(yè)，共62頁(yè)。圖168亮氨酸拉鏈(llin)第46頁(yè)/共62頁(yè)第四十七頁(yè)，共62頁(yè)。Major classes of transcription factors. Twelve distinct families of transcription factors have been classified by their DNA-binding motifs. Four examples of these transcription factors implicated in the contro

19、l of cell proliferation and differentiation are depicted here. Conserved regions unique to each family include regions of basic amino acids functioning as DNA-binding sites (solid rectangles) and putative helical regions associated with DNA binding or dimerization (cylinders) are shown. Transcriptio

20、nal activation domains (solid triangles) are generally not conserved even within a family, generating considerable diversity of functional transactivation among interacting family members. Each family has at present more than half a dozen members. The classes shown possess a POU domain (Pituitary-1,

21、 pit-1), a basic helix-loop-helix domain (HLH, MyoD), a nuclear receptor type of zinc-finger domain (glucocorticoid receptors), or the basic region/leucine zipper domain (bZIP; CCAAT/enhancer binding proteins, C/EBP). 第47頁(yè)/共62頁(yè)第四十八頁(yè)，共62頁(yè)。One type of zinc finger protein. This protein belongs to the C

22、ys-Cys-His-His family of zinc finger proteins, named after the amino acids that grasp the zinc. This zinc finger is from a frog protein of unknown function. (A) Schematic drawing of the amino acid sequence of the zinc finger. (B) The three-dimensional structure of the zinc finger is constructed from

23、 an antiparallel sheet (amino acids 1 to 10) followed by an a helix (amino acids 12 to 24). The four amino acids that bind the zinc (Cys 3, Cys 6, His 19, and His 23) hold one end of the a helix firmly to one end of the b sheet. 第48頁(yè)/共62頁(yè)第四十九頁(yè)，共62頁(yè)。DNA binding by a zinc finger protein. (A) The struc

24、ture of a fragment of a mouse gene regulatory protein bound to a specific DNA site. This protein recognizes DNA using three zinc fingers of the Cys-Cys-His-His type arranged as direct repeats. (B) The three fingers have similar amino acid sequences and contact the DNA in similar ways. In both (A) an

25、d (B) the zinc atom in each finger is represented by a small sphere. 第49頁(yè)/共62頁(yè)第五十頁(yè)，共62頁(yè)。Interaction between DNA and proteins containing zinc fingers.(a) GL1 is a monomeric protein that contains five C2H2 zinc fingers. -Helices are shown as cylinders, Zn+2 ions as spheres. Finger 1 does not interact

26、with DNA, whereas the other four fingers do. (b) The glucocorticoid receptor is a homodimeric C4 zinc-finger protein. -Helices are shown as purple ribbons, -strands as green arrows, Zn+2 ions as spheres. Two helices (darker shade), one in each monomer, interact with the DNA. Like all C4 zinc-finger

27、homodimers, this transcription factor has two fold rotational symmetry; the center of symmetry is shown by the yellow ellipse. In contrast, heterodimeric nuclear receptors do not exhibit rotational symmetry.第50頁(yè)/共62頁(yè)第五十一頁(yè)，共62頁(yè)。The Helix-Turn-Helix Motif Also Mediates Dimerization and DNA Binding The

28、 DNA-binding helix-turn-helix motif. The motif is shown in (A), where each white circle denotes the central carbon of an amino acid. The carboxyl-terminal a helix (red) is called the recognition helix because it participates in sequence-specific recognition of DNA. As shown in (B), this helix fits i

29、nto the major groove of DNA, where it contacts the edges of the base pairs 第51頁(yè)/共62頁(yè)第五十二頁(yè)，共62頁(yè)。Some helix-turn-helix DNA-binding proteins. All of the proteins bind DNA as dimers in which the two copies of the recognition helix (red cylinder) are separated by exactly one turn of the DNA helix (3.4 nm

30、). The second helix of the helix-turn-helix motif is colored blue. The lambda repressor and cro proteins control bacteriophage lambda gene expression, and the tryptophan repressor and the catabolite activator protein (CAP) control the expression of sets of E. coli genes. 第52頁(yè)/共62頁(yè)第五十三頁(yè)，共62頁(yè)。. (a) In

31、 leucine-zipper proteins, basic residues in the extended helical regions of the monomers interact with the DNA backbone at adjacent major grooves. The coiled-coil dimerization domain is stabilized by hydrophobic interactions between the monomers. (b) In bHLH proteins, the DNA-binding helices at the

32、bottom (N-termini of the monomers) are separated by nonhelical loops from a leucine-zipper-like region containing a coiled-coil dimerization domain.Interaction of homodimeric leucine-zipper and basic helix-loop-helix (bHLH) proteins with DNA第53頁(yè)/共62頁(yè)第五十四頁(yè)，共62頁(yè)。 Leucine zipper homodimers bind to symm

33、etric DNA sequences, as shown in the left-hand and center drawings. These two proteins recognize different DNA sequences, as indicated by the red and blue regions in the DNA. The two different monomers can combine to form a heterodimer, which now recognizes a hybrid DNA sequence, composed from one r

34、ed and one blue region. Transcription-Factor Interactions Increase Gene-Control Options alter their DNA-binding specificity. 第54頁(yè)/共62頁(yè)第五十五頁(yè)，共62頁(yè)。A homeodomain bound to its specific DNA sequence. The homeodomain is folded into three a helices, which are packed tightly together by hydrophobic interact

35、ions (A). The part containing helix 2 and 3 closely resembles the helix-turn-helix motif, with the recognition helix (red) making important contacts with the major groove (B). The Asn of helix 3, for example, contacts an adenine. Nucleotide pairs are also contacted in the minor groove by a flexible

36、arm attached to helix 1. The homeodomain shown here is from a yeast gene regulatory protein, but it is nearly identical to two homeodomains from Drosophila, which interact with DNA in a similar fashion. 第55頁(yè)/共62頁(yè)第五十六頁(yè)，共62頁(yè)。The binding of a gene regulatory protein to the major groove of DNA. Only a single type of contact is shown. Typically,