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1 Gene expression regulation *** Enmin Li 2  Section 1** Basic concept, specificity and modality of gene expression  Section 2** Basic principle of.

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Presentation on theme: "1 Gene expression regulation *** Enmin Li 2  Section 1** Basic concept, specificity and modality of gene expression  Section 2** Basic principle of."— Presentation transcript:

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2 1 Gene expression regulation *** Enmin Li

3 2  Section 1** Basic concept, specificity and modality of gene expression  Section 2** Basic principle of gene expression regulation  Section 3** Regulation of gene expression in prokaryote  Section 4** Regulation of gene expression in eukaryote

4 3 Section 1 The basic concept, specificity and modality of gene expression

5 4 1.1 The concept of gene expression gene expression transcription translation = +

6 5 DNAs RNAs Proteins 1 proteins 2 RNAs 1 proteins 2 RNAs Interaction among large biomolecules

7 6 1.2 The specificity of gene expression in the time and the space

8 7 1.2.1 The temporal specificity of gene expression  The temporal specificity is that some specific genes in genome are expressed in order of specific time  The temporal specificity is also stage specifi- city in the polycellular biosomes  The expressed genes in early developmental steps are more than in other steps in polycellular biosomes  The expressed genes relate with biological function.

9 8 1.2.2 The spatial specificity of gene expression  In the polycellular biosomes the spatial speci- ficity of gene expression is that one or some specific genes in the genome are expressed in different systems, organs, tissues and cells in order of space.  The spatial specificity of gene expression is also known as tissue specificity or cell specificity.  The expressed genes relate with biological function.

10 9 1.3 Modality of gene expression 1.3.1 Constitutive gene expression 1.3.2 Inductive and repressive gene expression

11 10 1.3.1 constitutive gene expression  Some genes in genome are known as housekeeping genes.  The expression of housekeeping genes in genome are also called constitutive gene expression.  Constitutive gene expression is continual in most cells.

12 11  The expressive products of constitutive genes are absolutely necessary in all over life process.  The expression of constitutive genes are less effected by environment factors.  The constitutive gene expression are only effected by interacting between promoter and RNA polymerase.

13 12 1.3.2 Inductive and repressive gene expression  The expression of some genes in genome are more effected by environment factors.  The increase of gene expression which is effected by environment factors are called induction, in contrast, the decrease of that are repression.

14 13  The expression of induced or repressed genes are regulated by other factors, besides interaction between promoter and RNA polymerase.  The special elements are located in the regulation region of induced or repressed genes.  Induction and repression of gene expression correspond with each other.

15 14 1.4 Biological significance of gene expression regulation  acclimation  keep growth and proliferation  keep individual development and differentiation

16 15 Section 2 Basic principle of gene expression regulation

17 16 2.1 multilevel regulation of gene expression check point v activity of gene structure in genome v DNA amplification v DNA rearangement v DNA methylation  initiation of RNA transcription*  process of RNA post-transcription  transport of RNA post-process  initiation of protein translation  process of protein post-translation

18 17 2.2 basic factors of gene expression regulation regulation protein RNA polymerase specific DNA sequence

19 18 -35 region -10 region 2.2.1 specific DNA sequence 2.2.1.1 promoter of prokaryotic genes spacer ATTTACATATGAT N7N7 N 16 ATTTACATATGTT N6N6 N 17 ATTGATATATAAT N7N7 N 16 ACTGACGTACTGT N6N6 N 18 ATTGACATTAACT N7N7 N 17 transcriptional initiation site tRNA Tyr trp lac recA ara BAC +1 “TTGACA”“TATAAT” consensus sequence

20 19 2.2.1.2 the prokaryotic operon  The concept of the operon was first proposed in 1961 by Jacob and Monod.  An operon is a whole unit of prokaryotic gene expression which includes a set of structural genes and its promoter, operator and other control elements which are recognized and bond by regulatory gene products.

21 20  The operator is a site bond with the repressor.  The operator mediates a negative regulation of operon.  The operator is next to the promoter.  The operator sites in downstream of the promoter.  The operator overlaps partly with the promoter some time. Regulatory region Inhibitor gene Gene 1Gene 2Gene 3 Structural genes region O p 3’3’ 5’5’ i gene region repressor RNA polymerase

22 21 2.2.1.3 Other regulator of prokaryotic operons  special DNA sequence in some prokaryotic operons  can bind with activator of RNA polymerase  increase transcription of operons  mediate positive regulation of operons  The positive regulation is not main mechanism about gene expression regulation of operons, but the negative regulation is.

23 22 2.2.1.4 cis-acting elements of eukaryotic gene  The cis-acting elements are DNA fragments.  The cis-acting elements are the regulator of eukaryotic gene transcription  There are cis-acting elements in the flakings or the introns of eukaryotic gene.  The cis-acting elements include promoter,enhancer, silencer and so on.

24 23 gene coding region enhancer silencer enhancer silencerpromoter 3’3’ 5’5’ exon intron exon RNA polymerase  The eukaryotic genes are monocistron.  there are not the operons structure in eukaryotic genome

25 24 2.2.2 regulation protein 2.2.2.1 regulation protein of prokaryotic genes  specific factors : decide identification and bind between RNA polymerase and specific promoter  repressor : bind operator and repress gene transcription  activator: bind a special DNA sequence next to promoter advance to bind between RNA polymerase and promoter and to form transcription initiation complex.

26 25 2.2.2.2 regulation protein of eukaryotic genes  transcription factor, it is also trans-acting factor.  cis-acting protein PBPB BPAPA A protein A trans-acting protein trans-acting factor protein B cis-acting protein trans-regulation cis-regulation

27 26 2.2.3 RNA polymerase 2.2.3.1 promoter of prokaryotes/eukaryotes effect on RNA polymerase  The promoter of prokaryotes/eukaryotes is consist of transcription initiation site, RNA polymerase identification and binding site and other regulation elements.  The promoter of eukaryotes is more complicated than that of prokaryotes.

28 27  The sequence of different promoter is certain different.  The affinity of prokaryotic promoter with RNA polymerase effects directly on frequency of gene transcription initiation  The affinity between eukaryotic RNA polymerase and promoter is less, when RNA polymerase is single.  The eukaryotic RNA polymerase can bind with promoter after forming complex with basic transcription factor.

29 28 2.2.3.2 regulation proteins effect on activity of RNA polymerase  Specific promoter decides basic transcription frequency of genes.  The regulation proteins can change transcription frequency of genes.  The conformation or the expression level in the cell of regulation proteins gets a change under stimulation of environment signal.

30 29 2.2.4 DNA-protein and protein-protein interaction in transcription regulation of eukaryotic genes 2.2.4.1 DNA-protein interaction  Identification and bind between cis-acting proteins or trans-acting factors and cis-acting elements  Its interaction is a non-covalent bond.  Form DNA-protein complex finally

31 30 2.2.4.2 protein-protein interaction  The most regulation protein can form homodimer, heterodimer, homopolymer or heteropolymer before binding with cis-acting element.  Ability of some regulation protein to bind with its cis-acting element is increased or decreased after polymerization.  Some regulation protein don’t bind with DNA, but can effect the activity binding between DNA and other regulation protein by protein-protein interaction.

32 31 Section 3 Regulation of prokaryotic gene expression 3.1 Characters of transcribed regulation in prokaryotic genes 3.2 Regulation of transcribed initiation in prokaryotic genes 3.3 Regulation of transcribed termination in prokaryotic genes 3.4 Regulation of proteic translation in prokaryote

33 32 3.1 characters of transcriptional regulation in prokaryotic genes 3.1.1 The function of  factors  The  factors bind a special element in 5’ flaking region of genes in the stage of transcribed initiation  The  factors decide the specificity of transcribed genes  The  factors mediate holoenzyme of RNA polymerase binding to specific promoter of genes  Different  factors decide transcription of different genes.

34 33 3.1.2 universality of operon model  the most prokaryotic genes  There are many operons in order in prokaryotic genome.  Don’t discover operon in eukaryotic genome. 3.1.3 universality of repression mechanism  The repression mechanism is the main mechanism of transcriptional regulation of prokaryotic genes

35 34 3.2 regulation of transcribed initiation in prokaryotic genes

36 35 3.2.1 stucture of lactose operon C regulatory region Inhibitor gene Gene ZGene YGene A structural genes region O p 3’3’ 5’5’ i gene region 1000bp 100bp 3520bp 760bp810bp base pair: peptide : (MW kDa) 37 repressor (4 polymer) 32 30 135  -galactosidase (4 polymer) lactose cell galactose + acetyl CoA acetylgalactose + glucose galactose lactose  - galactoside transacetylase (2 polymer) lactose permease (2 polymer)

37 36 Catabolite gene activation protein site - 10 site - 35 site CACCCCAGGCTTTACACTTTATGCTTCCGGCTCGTATGTTGTGTGGAATTGAGCGGA TAACAATTTCACACTAACAATTTCACAC CTCATTAGGCTCATTAGG ACTCGATTGAGTGTAATTA 5’ 3’ Operon region 20bp RNA polymerase binding region or promoter region Primary structure of lac operon regulation region 5’ TATAAT 3’ Pribnow box

38 37 z y ai o p repressor (4 polymer) RNA polymerase z y ai o p repressor (4 polymer) RNA polymerase + galactose mRNA 3.2.2 regulated mechanism of lac operon genes 3.2.2.1 repressor regulate negatively transcription of lac operon genes

39 38 3. 2.2.2 catabolite gene activation protein(CAP) regulate positively transcription of lac operon genes CAP site - 35 - 10 1 5’ 3’ RNA polymerase - 35 - 10 CAP cAMP at glucose absents CAP cAMP CAP + at glucose presents

40 39 3.2.3 correspond between negative regulation of repressor and positive regulation of CAP in gene transcription control of lac operon CAP site 0 5’ 3’ - 35 - 10 RNA polymerase inhibitor gene 3.2.3.1 glucose concentration is lower and lactose concentration is higher Repressor (4 polymer) + galactose cAMP at glucose absents CAP cAMP CAP + cAMP

41 40 CAP site 0 5’ 3’ - 35 - 10 RNA polymerase inhibitor gene cAMP at glucose presents CAP cAMP CAP + 3.2.3.2 glucose concentration is higher and lactose concentration is lower Repressor (4 polymer)

42 41 The negative regulation mechanism of the repressor cooperate with the positive regulation mechanism of the CAP control gene transcription of lac operon by kind and concentration of carbohydrate from the environment.

43 42 3.3 regulation of transcribed termination in prokaryotic genes

44 43  5’ c 3.3.1 Dependent upon  factor 5’ Promoter Gene RNA polymerase Terminator c new RNA 

45 44 RNA polymerase 5’ coding strand template strand new RNA transcript 3.3.2 model about transcription termination for independent to  factor

46 45 GACCGCCGGACCGCCG CUGGCGGCCUGGCGGC A U U U U-OH 3’5’ U U C G G 5’…GCCGCCAGUUCGGCUGGCGGCAUUUU…3’ RNA 5’…GCCGCCAGTTCGGCTGGCGGCATTTT… 3’terminator  The RNA made from the DNA palindrome is self- complementary and so formed a internal hairpin structure followed by a few U bases.  The signals that terminates transcri- ption are localized in the gene 3’ end.  A simple termination signal is a GC- rich region that is a palindrome, followed by AT-rich sequence. DNA

47 46 Synthesis of tryptophan in E. coli O HO H2CH2C COOH C Chorismic acid COOH NH 2 Anthranilic acid synthetase CH 2 N CH OH O P CH Indolglycerol phosphate Indoglycerol phosphate synthetase NH 2 N CH CH 2 COOH Tryptophan synthetase 3.3.3 attenuation regulation mechanism of gene transcription of trp operon in E.coli L Trp operon REDCBA p O Attenuater

48 47 The regulation mechanism of trp operon at a few tryptophans present or tryptophans absent L Inactive repressor REDCBA p O whole mRNA at a lot of tryptophans present L Inactive repressor Trp + Repressor REDCBA p O RNA polymerase or fragmentary mRNA

49 48 M K A I F L K G 1 2 3 4 ribosome Try code RNA polymerase RNA DNA M K A I F L K G 1 3 4 ribosome Try code RNA polymerase 2 W W R DNA RNA tryptophans absent lot of tryptophans

50 49 3.4 regulation of proteic translation in prokaryote

51 50 3.4.1 autoregulation/autogenous control Protein mRNA DNA same mRNA 5’ 3’ started region

52 51 3.4.2 antisene control Protein mRNA DNA 5’ 3’ started region Antisens RNA

53 52 Section 4 Regulation of eukaryotic gene expression 4.1 character of eukaryotic genomic structure 4.2 character of expressional regulation of eukaryotic genes 4.3 regulation of transcription for RNA pol I and RNA pol III 4.4 regulation of transcriptional initiation for RNA pol II 4.5 regulation of transcriptional termination for RNA pol II 4.6 regulation of past-transcription for RNA 4.7 regulation of translation for protein

54 53 4.1 Character of eukaryotic genomic structure  The eukaryotic genome is very great.  The structure of eukaryotic genome is very complex.  There is only a gene in a transcriptional unit of eukaryotic genome.  There are a lot of repeat sequences in eukaryotic genome.  Gene are discontinuous, there are noncoding sequences in the most eukaryotic gene.

55 54 4.2 character of transcription regulation of eukaryotic genes 4.2.1 three RNA polymerases in eukaryote  RNA polymerase Ⅰ, 45s-rRNA(28S, 18S, 5.8S)  RNA polymerase Ⅱ * , hnRNA(mRNA), a part of snRNA  RNA polymerase Ⅲ, 5s-rRNA, tRNA, a part of snRNA

56 55  The every RNA polymerase is consist of about 10 subunits.  The some subunits are in common for every RNA polymerase, for example TATA box-binding protein (TBP).  The some subunits are special for a RNA polymerase.  TF Ⅱ D is core of polymerase Ⅱ.  TF Ⅱ D is consist of TBP and TBP-related factor.

57 56 4.2.2 structural character of active gene region  There are hypersensitive sites of DNase Ⅰ in the flanking regions of active gene, near regulation protein binding sites. Gene coding region Promoter Silencer or Enhancer Silencer or Enhancer site

58 57 DNA RNA

59 58 dsDNA supersolenoid chromatid chromosome solenoid chromatin nucleosomes transcription bubble RNA activity of gene structure 213456

60 59  When gene is activated, topology structure of transcription region DNA in front of RNA polymerase is positive superhelix conformation,that one in back of RNA polymerase is negative superhelix conformation. RNA polymerase negative superhelix positive superhelix

61 60 GCGCGCGC  The negative superhelix conformation of DNA is propitious to form nucleosomes again, positive one is propitious to separate histone in nucleosomes  The methylation of CpG sequence in active gene flaking region is lower. Gene

62 61  The histons in active gene region change often as follows:  The histons is prone to be modified, in result its structure becomes instability.  The dimer H2A-H2B is prone to be replaced out from nucleosome.  The instability of dimer H2A-H2B is increased.  The rich-Lys H1-like histons are decreased.

63 62 4.2.3 The positive regulation is main in gene transcription regulation of eukaryotes  The most transcriptional regulation proteins are transcription activation proteins.  The affinity between RNA polymerase and promoter in eukaryotes is very weaker or not.  RNA polymerase must depend on one or many activation proteins to bind with promoter.  The positive regulation is universality in gene transcription regulation of eukaryotes.

64 63  The eukaryotic genome is very great.  There are many cis-acting elements in a gene regulation region, in result that specificity of interaction between activation protein and DNA is increased.  Many activation proteins regulate a gene, therefore the regulation efficiency is higher.  A activation proteins regulate many gene, therefore the regulation is more economical.

65 64 4.2.4 The transcription and the translation are separated in different area, this is prone to regulate exactly in gene transcription 4.2.5 The process of post-transcription modification is more complex and perfect, therefore links of gene expression regulation is increased.

66 65 4.3 regulation of transcription for RNA pol Ⅰ and RNA pol Ⅲ

67 66 4.3.1 control of transcription for RNA pol Ⅰ rDNA gene -45 +20-156 -107 core elementupstream control element rRNA RNA pol Ⅰ upstream binding factor 1, UBF-1 selectivity factor 1, SL-1 RNA pol Ⅰ

68 67 4.3.2 control of transcription for RNA pol Ⅲ TGGCNNAGTGGGGTTCGANNCC TGGCNNAGTGGGGTTCGANNCC tRNA +1 TGGCNNAGTGG tDNA gene GGTTCGANNCC TGGCNNAGTGGGGTTCGANNCC TF Ⅲ C RNA pol Ⅲ TF Ⅲ B

69 68 TGGCNNAGTGGGGTTCGANNCC TGGCNNAGTGGGGTTCGANNCC tRNA +1 TGGCNNAGTGG tDNA gene GGTTCGANNCC TGGCNNAGTGGGGTTCGANNCC TF Ⅲ C RNA pol Ⅲ TF Ⅲ B

70 69 5s rRNA +1 5s rDNA gene RNA pol Ⅲ TF Ⅲ A TF Ⅲ C TF Ⅲ B

71 70 4.4 regulation of transcriptional initiation for RNA pol Ⅱ

72 71 4.4.1 cis-acting element according to function, main including promoter, enhancer, silencer and so on

73 72 gene coding region enhancer silencer enhancer silencerpromoter 3’3’ 5’5’ exon intron exon RNA polymerase

74 73 4.4.1.1 promoter  It is consist of RNA polymerase binding site, a set of other functional elements which control transcription and a transcription initiation site at least.  The length of every functional elements in the promoter is about 7-20 bp.  Promoter sequence of different genes is a little different.  Most gene promoter sequence have TATA box.

75 74  TATA box is the most basic and important functional element in the promoter.  The consensus sequence of TATA box is TATAAAA locating in -25  -30 bp region of transcription start site upstream.  TATA box controls veracity and frequency of gene transcription.  GC box ( GGGCGG ) and CAAT box ( GCCAAT ) is more frequent in the promoter.  GC box and CAAT box locate in -30  -110 bp region of transcription start site upstream.

76 75  The promoter locates in upstream of coding region of the gene certainly.  The promoter has strict direction.  The most simple promoter is consist of TATA box and transcription start site, but the typical promoter often contains also GC box and/or CAAT box in upstream of TATA box.

77 76  The promoter of some genes don’t contain TATA box.  The promoter without TATA box always contains many transcription start sites, and contains rich-GC sometimes.  The gene that contains the promoter without TATA box is house keeping gene or the gene which plays a role in fetation, tissue differentiation, tissue damage regeneration and so on.

78 77 4.4.1.2 enhancer  The enhancer is a DNA fragment.  The enhancer increases activation of gene transcription and decides space-time specificity of gene transcription. gene enhancer 5’ 3’ 72bp enhancer core sequence TGTGGAATTAG

79 78  The role of the enhancer don’t relate with its distance from transcription start site. The enhancer is very far from gene transcription start site(1~30/50kb) and locates not only in genic upstream, but also in genic downstream, sometimes in the intron.  Some important functional elements , for example core DNA sequence which is bond with special transcription factors, is in the enhancer and the promoter at same time. TATA box Enhencer-1 - 200 Enhancer-3 +10kb to +50kb Enhancer-2 - 10kb to - 50kb Gene regulatory proteins Gene regulatory proteins gene 5’ 3’ RNA pol II transcription initiation complex

80 79 promoterenhancergene  The enhancer always interlinks or overlaps with the promoter.  Sometimes the enhancer and the promoter too close in structure to differentiate definitely in space and function.  The DNA structure of both the promoter and the enhancer is called space-time special promoter. space-time special promoter

81 80 Control of gene expression  The action of enhancer is not strict specific. enhancer regulatory protein promoter transcription initiation complex 1 promoter transcription initiation complex 2 promoter transcription initiation complex n

82 81  The action of enhancer does not have strict direction. promoter gene 5’ 3’ GCGA…GCT ACGT...ACG enhancer gene 5’ 3’ TCG...AGCG GCA...TGCA  

83 82 4.4.1.3 silencer  The silencers are the negative elements in gene transcription regulation, in contrast to the enhancers.  The gene transcription is suppressed when specific regulation protein have bound with the silencers.  Some silencers play the role of enhancers sometime this mainly depends to the character of regulation proteins in the nucleus.

84 83 4.4.2 transcription regulation factors  The transcription regulation factors are also called transcription factors (TF).  Most transcription regulation factors are trans-acting factors, a few ones are cis- acting proteins.

85 84 TATA box various control element - 200 silencer +10kb to +50kb enhancer - 10kb to - 50kb gene 5’ 3’ RNA pol II transcription initiation complex Control of gene expression Trans-acting factor Gene regulatory proteins Gene regulatory proteins

86 85 4.4.2.1 type of transcription factors 4.4.2.1.1 general transcription factors  It is necessary for the RNA polymerase bind with the promoter.  It decides RNA transcription type.  It is also regarded as a component of RNA polymerase.

87 86 Various transcription factors of RNA polymerase II TFMolecular weitht, kDFunction TF II A12, 19, 35 stabilize TF II D TF II B 33 accelerate that RNA pol II binding with DNA. TF II DTBP/38, TAP/15-250recognize TATA box TF II E 57(  ), 34(  ) ATPase TF II F30, 74 helicase TF II I120 accelerate that TF II D binding TATA TF II H35-89phosphorylation of carboxyl terminal domain of RNA pol II large subunit

88 87 4.4.2.1.2 special transcription factors  It is necessary for individual gene transcription.  It decided the specificity of gene transcription in the time and the space.  Most special transcription factors are transcription activators, a few ones are transcription inhibitors.

89 88  Most transcription activators are the proteins binding with the enhancer.  Most transcription inhibitors are the proteins binding with the silencer.  Some transcription inhibitors don’t directly interact with DNA, but bind with the general transcription factor II-D or some transcription activators and decrease effective concentration of the latter in cell and suppress gene transcription.

90 89 4.4.2.2 structure of transcription factor  Usually, a transcription factor contains a DNA binding domain and a transcription activation domain.  Many transcription factors also contain a domain which mediate protein-protein interaction, for example dimerization domain.

91 90 4.4.2.2.1 DNA binding domain  It is consist of 60~ 100 amino acid residues usually.  the most familiar structures:  zinc finger structure  basic  - helix structure  other structures:  basic leucine zipper structure , bZIP  basic helix-turn helix structure , bHTH  basic helix-loop-helix structure , bHLH

92 91 zinc finger in TF III A C + C C C + + + + + + + + ++ + + + + + + + + Zn C + C H H + + + + + + + ++ + + + + + + + + C Y C H H + + + + L + + ++ F + + + + + + + ++ + COOH H2NH2N zinc finger in SP1 ( TF ) bind with GC box , discovered the zinc finger early

93 92 Zn

94 93 basic  - helix domain(bAH) DNA binding domain of CTF1 (transcription factor)

95 94 basic leucine zipper , bZIP COOH NH 2 COOH NH 2 18 15 22 29 36 1 8 15 22 29 36 Leucine residue C N C O H CH 2 CH CH 3

96 95 basic helix-turn helix , bHTH 3.4nm 2 1 3 + 2 1 3 2 1 3 2 1 3 2 1 3 2 1 3 -phage Cro

97 96 basic helix-loop-helix , bHLH 2 1 3

98 97 4.4.2.2.2 transcription activation domain  It is usually consist of 30  100 amino acid residues.  It is divided three types as follows:  acidic activation domain  glutamine-rich domain  proline-rich domain

99 98 4.4.2.2.3 dimerization domain It is the basic leucine zipper or basic helix loop helix in protein structure.

100 99 cis-acting elements the structure of gene in eukaryote, cis-acting element and trans or cis -acting factor exon intron ATG TAA Poly A site AATAAA, 30bp downstream enhancer terminator downstream silencer initiation site promoter upstream silencer upstream enhancer coding strand template strand 5’ 3’ 12n 12 n-1 TATA boxCAAT box GC box trans or cis-acting factors

101 100 gene TATA enhancer mRNA transcription activation and regulation 5’ 3’ promoter region EBP TF II A pol II TF II F TBP TAF TF II E TF II B

102 101 gene TATA enhancer 5’ 3’ promoter region EBP TF II A pol II TF II F TATA TAF TF II A pol II / TF II F PIC TBP TF II B TF II E TIC EBP enhancer TBP TAF TF II E TF II B

103 102 RNA dsDNA supersolenoid chromatid chromosome solenoid chromatin nucleosomes Transcription bubble activity of gene structure 2 1 3456 8 9 10 11 AAAAAAAAAA hnRNA 7 protein precursor rRNAprecursor rRNA Mature tRNAprecursor tRNA Mature 12 protein mature 13 mRNA Mature 14 16 amino acid polysome 15 function multilevel regulation of gene expression

104 103 练 习 题 四 1 基因表达的产物可以是 A DNA B tRNA C mRNA D rRNA E 蛋白质 F hnRNA

105 104 2 基因表达的组织特异性可表现为 A 不同基因在同一组织中表达不同 B 同一基因在不同组织中表达不同 C 不同基因在不同组织中表达不同 D 不同基因在同一组织中表达相同 E 同一基因在不同组织中表达相同

106 105 3 直接参与乳糖操纵子调控的因素是 A I 基因编码蛋白 B Z 基因编码蛋白 C CAP D Y 基因编码蛋白 E 乳糖

107 106 4 参与原核基因表达调控的因素是 A 激活蛋白 B 阻遏蛋白 C 某些小分子化合物 D 基本转录因子

108 107 5 基因表达调控可以发生在 A 转录起始水平 B 转录水平 C 转录后加工水平 D 翻译起始水平 E 翻译水平 F 翻译后加工水平 G 复制水平

109 108 6 顺式作用元件是下述的 A TATA 盒和 CCAAT 盒 B 具有调节功能的各种 DNA 序列 C 具有调节功能的 5’ 侧翼序列 D 具有调节功能的 3’ 侧翼序列 E 所有非编码序列

110 109 7 反式作用因子是 A 转录调节蛋白 B 转录调节因子 C RNA 聚合酶 D DNA 聚合酶 E DNA 酶 I

111 110 8 真核基因表达调控的特点是 A 正性调节占主导 B 伴有染色体结构变化 C 转录与翻译分隔进行 D 转录与翻译偶联进行 E 负性调节占主导

112 111 9 乳糖操纵子 A 在没有半乳糖存在时处于阻遏状态 B 在半乳糖存在时可能处于表达状态 C 有高浓度半乳糖、低浓度葡萄糖存在时处于 表达状态 D 有半乳糖存在时处于阻遏状态 E 没有半乳糖存在时处于表达状态

113 112 10 可影响 RNA 聚合酶活性的因素是 A 启动子或启动序列 B 调节蛋白的性质 C RNA 转录本的结构 D RNA 转录本的长度 E 多聚 A 序列的长度

114 113 11 基因表达具有 A 阶段特异性 B 组织特异性 C 细胞特异性 D 时间特异性 E 空间特异性

115 114 12 原核基因表达调控的意义是 (只有一个正确答案) A 调节生长与分化 B 调节发育与分化 C 调节生长、发育与分化 D 调节代谢,适应环境 E 维持细胞特性和调节生长

116 115 13 真核基因表达调控的意义是 (只有一个正确答案) A 调节代谢,维持生长 B 调节代谢,维持发育与分化 C 调节代谢,发育与分化 D 调节代谢,适应环境 E 调节代谢,适应环境,维持生长、发育与分化

117 116 14 下述关于管家基因表达的描述最确切的是 (只有一个正确答案) A 在生物个体的所有细胞中表达 B 在生物个体生命全过程几乎所有细胞中持续表达 C 在生物个体生命全过程部分细胞中持续表达 D 特定环境下, 在生物个体生命全过程几乎所有细 胞中持续表达 E 特定环境下,在生物个体生命全过程部分细胞中 持续表达

118 117 15 基本的基因表达 (只有一个正确答案) A 有诱导剂存在时表达水平增高 B 有诱导剂存在时表达水平降低 C 有阻遏剂存在时表达水平增高 D 有阻遏剂存在时表达水平降低 E 极少受诱导剂或阻遏剂的影响

119 118 16 紫外线照射引起 DNA 损伤时,细菌 DNA 修复酶 基因表达增强,这种现象被称为 (只有一个正确答案) A 诱导 B 阻遏 C 基本的基因表达 D 正反馈 E 负反馈

120 119 17 大多数基因表达调控的最基本环节是 (只有一个 正确答案) A 复制水平 B 转录水平 C 转录起始水平 D 转录后加工水平 E 翻译水平

121 120 18 顺式作用元件的最确切定义是 (只有一个正确答案) A TATA 盒和 CCAAT 盒 B 具有调节功能的各种 DNA 序列 C 具有调节功能的 5’ 侧翼序列 D 具有调节功能的 3’ 侧翼序列 E 所有非编码序列

122 121 19 对乳糖操纵子来说 (只有一个正确答案) A CAP 是正性调节因素,阻遏蛋白是负性调节因素 B CAP 是负性调节因素,阻遏蛋白是正性调节因素 C CAP 和阻遏蛋白都是正性调节因素 D CAP 和阻遏蛋白都是负性调节因素 E 在不同条件下, CAP 和阻遏蛋白均显示正性 或负性调节特点

123 122 20 一个操纵子通常含有 (只有一个正确答案) A 一个启动序列和一个编码基因 B 一个启动序列和数个编码基因 C 数个启动序列和一个编码基因 D 数个启动序列和数个编码基因 E 一个启动序列和数个调节基因


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