Chapter 11 Phage strategies 莘大
Chapter 11 Phage strategies
11.1 Introduction 11.2 Lytic development is divided into two periods 11.3 Lytic development is controlled by a cascade 11. 4 Functional clustering in phages T7 and T4 11.5 Lambda immediate early and delayed genes are needed for both lysogeny and the lytic cycle 11. 6 The lytic cycle depends on antitermination 11.7 Lysogeny is maintained by repressor protein 11. 8 Repressor maintains an autogenous circuit 1.9 The repressor and its operators define the immunity region 11.10 The DNA-binding form of repressor is a dimer 11 11 Repressor uses a helix-turn-helix motif to bind dna 11 12 Repressor dimers bind cooperatively to the operator 11.13 Repressor at OR2 interacts with RNa polymerase at PRM 11 14 The cll and clli genes are needed to establish lysogeny 11. 15 PRE is a poor promoter that requires cll protein 11.16 Lysogeny requires several events 11. 1 7 The cro repressor is needed for lytic infection 消当 11.18 What determines the balance between lysogenic and the lytic cycle?
11.1 Introduction 11.2 Lytic development is divided into two periods 11.3 Lytic development is controlled by a cascade 11.4 Functional clustering in phages T7 and T4 11.5 Lambda immediate early and delayed genes are needed for both lysogeny and the lytic cycle 11.6 The lytic cycle depends on antitermination 11.7 Lysogeny is maintained by repressor protein 11.8 Repressor maintains an autogenous circuit 11.9 The repressor and its operators define the immunity region 11.10 The DNA-binding form of repressor is a dimer 11.11 Repressor uses a helix-turn-helix motif to bind DNA 11.12 Repressor dimers bind cooperatively to the operator 11.13 Repressor at OR2 interacts with RNA polymerase at PRM 11.14 The cII and cIII genes are needed to establish lysogeny 11.15 PRE is a poor promoter that requires cII protein 11.16 Lysogeny requires several events 11.17 The cro repressor is needed for lytic infection 11.18 What determines the balance between lysogenic and the lytic cycle?
11.1Introduction Episome is a plasmid able to integrate into bacterial dNA epistasis Immunity in phages refers to the ability of a prophage to prevent another hage of the same type from infecting a cell. It results from the synthesis of phage repressor by the prophage genome Induction refers to the ability of bacteria(or yeast) to synthesize certain enzymes only when their substrates are present; applied to gene expression refers to switching on transcription as a result of interaction of the inducer with the regulator protein Lysogeny describes the ability of a phage to survive in a bacterium as a stable prophage component of the bacterial genome Lytic infection of bacteria by a phage ends in destruction of bacteria and release of progeny phage Plasmid is an autonomous self-replicating extrachromosomal circular DNA Prophage is a phage genome covalently integrated as a linear part of the bacterial chromosome 请莘大
Episome is a plasmid able to integrate into bacterial DNA. Epistasis Immunity in phages refers to the ability of a prophage to prevent another phage of the same type from infecting a cell. It results from the synthesis of phage repressor by the prophage genome. Induction refers to the ability of bacteria (or yeast) to synthesize certain enzymes only when their substrates are present; applied to gene expression, refers to switching on transcription as a result of interaction of the inducer with the regulator protein. Lysogeny describes the ability of a phage to survive in a bacterium as a stable prophage component of the bacterial genome. Lytic infection of bacteria by a phage ends in destruction of bacteria and release of progeny phage. Plasmid is an autonomous self-replicating extrachromosomal circular DNA. Prophage is a phage genome covalently integrated as a linear part of the bacterial chromosome. 11.1 Introduction
11.1 Introduction i Phage DNA Figure ll I Lytic Bacterial DN ■■■ development involves LYTIC C YCLE LYSOGENY the reproduction of phage particles with destruction of the host Phage DNA is rated into bacterial genome bacteria live happily ever after bacterium, but lysogenic ■■■■■ existence allows the from I phage genome to be carried as part of the ogenic bacterium is im mune to further in fection bacterial genetic INDUCTION information 请莘大
Figure 11.1 Lytic development involves the reproduction of phage particles with destruction of the host bacterium, but lysogenic existence allows the phage genome to be carried as part of the bacterial genetic information. 11.1 Introduction
11.1 Introduction Type of Unit Genome Structure Mode of propagation Consequences Lytic phage dsor ss-DN A or RNA Infects susceptible host Usually kills host linear or circular Lysogenic phage ds-DNA Linear sequence in Im munity to infection host chromosome Plasmid ds-DNA cirde Replicates at defined Im munity to plasmids May be transmissible In same group Episome ds-DNA circle Free circle or linear integrated Ma ay transfer host dna Figure 11.2 Several types of independent genetic units exist in bacteria 消当
Figure 11.2 Several types of independent genetic units exist in bacteria. 11.1 Introduction
Pha 11.2 Lytic development sectio is controlled by a Phai taches to bacterium cascade acterium Ean mes for ynthesis are made Replication Figure 11.3 Lytic begins development takes place by Late development Genomes producing phage genomes heads. tails are made and protein particles that DNA packaged into heads tails attached are assembled into progeny pl ha ages 消当
Figure 11.3 Lytic development takes place by producing phage genomes and protein particles that are assembled into progeny phages. 11.2 Lytic development is controlled by a cascade
Early: phage genes are transcr bed by host RNA polymerase 11.2 Lytic development is controlled by a AAA cascade Types of gene product Regul ator gene(s) RNA polymerase gma factor or antiteminat on factor Middle: early product causes transcript on of middle genes Figure 11. 4 Phage lytic development Regul ator gene(s) proceeds by a regulatory sigma fa ctor or antite minat on factor cascade, in which a gene Structural genes Replicat ion enzymes etc product at each stage is Late: middle product causes transcription of late genes needed for expression of the genes at the next stage d. Structural genes 请莘大 Phage components
Figure 11.4 Phage lytic development proceeds by a regulatory cascade, in which a gene product at each stage is needed for expression of the genes at the next stage. 11.2 Lytic development is controlled by a cascade
EARLY INITIATION 11.2 Lytic development 入人A is controlled by a cascade EARLY TERMINATION Figure 9.31 Switches in Early region Next region transcriptional specificity can be RNA controlled at initiation ANTITERMINATION or termination 消当 Early/next joint mRI
Figure 9.31 Switches in transcriptional specificity can be controlled at initiation or termination. 11.2 Lytic development is controlled by a cascade
11.3 Functional Class Class I C|assⅢl clustering in phages T and T4 6 genes 7 genes 13 genes RNA polymerase ■■■■■■■ Host interference Figure 11. 5 Phage T7 contains thre ee classes DNA synthesis ■■■■■ of genes that are isozyme expressed sequentially. The Heads tails genome Is-38 kb DNA maturation 消当
Figure 11.5 Phage T7 contains three classes of genes that are expressed sequentially. The genome is ~38 kb. 11.3 Functional clustering in phages T7 and T4
11.3 Functional clustering in phages T7 and T4 F late RNA 55 The map of T4 late RNA 45 th thymidine kinase Is cIrcular de v endonucle ase v 42,43,62,44 iAl, ip. f internal proteins There is DNA polymerase etc e lysozyme 57 tail fiber extensive he ad 1 dNmP kin ase clustering of 3 sheath termin ator 58.61.41 2head completion genes coding DNA pr imase so head completion 65 head completion 5 baseplate plug components of topoisomerase 3 the phage and Ok b 6,7.8.9,10.12 rAn/8 processes such baseplate wedge topoisomerase aS dna wac,13.14.16. plication, but 837.363 head there is also tail fibers 120 dispersion of late RNA 18 sheath, 19tai d tMP synthetase genes coding 20.67,6.21,22,2 for a variety of DNA ligase 30 baseplate5982.51,2626 24. hoc inh he ad enzymatic and other functions baseplate plug Essential genes are indicated by numbers. Nonessential genes are identified by 请第大: I letters. Only some representative T.4 genes are shown on the map
Essential genes are indicated by numbers. Nonessential genes are identified by letters. Only some representative T4 genes are shown on the map. 11.3 Functional clustering in phages T7 and T4 Figure 11.6 The map of T4 is circular. There is extensive clustering of genes coding for components of the phage and processes such as DNA replication, but there is also dispersion of genes coding for a variety of enzymatic and other functions
