Transcription Figure: 11-01 Title: One strand is transcribed into RNA Caption: RNA is transcribed from the template strand of duplex DNA.

Figure: 11-02 Title: Promoters and terminators define the unit Caption: A transcription unit is a sequence of DNA transcribed into a single RNA, starting at the promoter and ending at the terminator.

Bubble length : 12-14 bp RNA-DNA hybrid : 8-9 bp Figure: 11-03 Title: RNA synthesis occurs in the transcription bubble Caption: DNA strands separate to form a transcription bubble. RNA is synthesized by complementary base pairing with one of the DNA strands. RNA-DNA hybrid : 8-9 bp

Figure: 11-05 Title: RNA polymerase surrounds the bubble Caption: During transcription, the bubble is maintained within bacterial RNA polymerase, which unwinds and rewinds DNA, and synthesizes RNA.

The overall reaction rate is - 40 nucleotides/second at 37oC Whereas Rate of DNA replication is 800 bp / sec. Figure: 11-04 Title: The transcription bubble moves along DNA Caption: Transcription takes place in a bubble, in which RNA is synthesized by base pairing with one strand of DNA in the transiently unwound region. As the bubble progresses, the DNA duplex reforms behind it, displacing the RNA in the form of a single polynucleotide chain.

Figure: 11-06 Title: RNA polymerase catalyzes transcription Caption: Transcription has several stages. RNA polymerase binds to the promoter and melts DNA, remains stationary during initiation, moves along the template during elongation, and dissociates at termination.

Figure: 11-10 Title: The active site holds the transcription bubble Caption: DNA is forced to make a turn at the active site by a wall of protein. The RNA-DNA hybrid has bases flipped out of the helix. Its length is limited by the rudder. Nucleotides enter through a pore in the protein.

Figure: 11-13 Title: b and b' subunits contact DNA and RNA Caption: Both the template and coding strands of DNA are contacted by the b and b' subunits largely in the region of the transcription bubble and downstream. The RNA is contacted mostly in the transcription bubble.

Core enzyme binds indiscriminately to any DNA. Sigma factor reduces the affinity for sequence – independent binding, confers specificity for promoters Figure: 11-14 Title: Sigma factor controls specificity Caption: Core enzyme binds indiscriminately to any DNA. Sigma factor reduces the affinity for sequence-independent binding, and confers specificity for promoters.

A closed binary complex is converted to an open form and then into a ternary complex Figure: 11-17 Title: There are several stages in initiation Caption: RNA polymerase passes through several steps prior to elongation. A closed binary complex is converted to an open form and then into a ternary complex.

Figure: 11-18 Title: Sigma and core enzyme must dissociate Caption: Sigma factor and core enzyme recycle at different points in transcription.

Promoter recognition depends on consensus sequences Figure: 11-19 Title: The promoter has three components Caption: A typical promoter has three components, consisting of consensus sequences at -35 and -10 and the startpoint.

Figure: 11-20 Title: RNA polymerase contacts one face of DNA Caption: One face of the promoter contains most of the contact points for RNA (shown by circles on the DNA strands). The initial region of unwinding extends from within the -10 sequence to past the startpoint.

Figure: 11-21 Title: Contact --> binding --> melting Caption: The -35 sequence is used for initial recognition, and the -10 sequence is used for the melting reaction that converts a closed complex to an open complex.

Figure: 11-22 Title: Transcription changes DNA structure Caption: Transcription generates more tightly wound (positively supercoiled) DNA ahead of RNA polymerase, while the DNA behind becomes less tightly wound (negatively supercoiled).

Figure: 11-23 Title: Sigma controls promoter recognition Caption: The sigma factor associated with core enzyme determines the set of promoters at which transcription is initiated.

Figure: 11-24 Title: E. coli has several sigma factors Caption: In addition to s70 E. coli has several sigma factors that are induced by particular environmental conditions.

Figure: 11-27 Title: s entends along the core surface Caption: Sigma factor has an elongated structure that extends along the surface of the core subunits when the holoenzyme is formed.

Figure: 11-31 Title: Bacterial termination occurs at a discrete site Caption: The DNA sequences required for termination are upstream of the terminator sequence. Formation of a hairpin in the RNA may be necessary.

Figure: 11-32 Title: An intrinsic terminator has two features Caption: Intrinsic terminators include palindromic regions that form hairpins varying in length from 7-20 bp. The stem-loop structure includes a G·C-rich region and is followed by a run of U residues.

Figure: 11-33 Title: Rho terminates transcription Caption: Rho factor binds to RNA at a rut site and translocates along RNA until it reaches the RNA-DNA hybrid in RNA polymerase, where it releases the RNA from the DNA.

Figure: 11-35 Title: A rho hexamer translocates along RNA Caption: Rho has an N-terminal RNA-binding domain and a C-terminal ATPase domain. A hexamer in the form of a gapped ring binds RNA along the exterior of the N-terminal domains. The 5' end of the RNA is bound by a secondary binding site in the interior of the hexamer.

Figure: 11-36 Title: Termination of transcript can be regulated Caption: Antitermination can control transcription by determining whether RNA polymerase terminates or reads through a particular terminator into the following region.

Figure: 11-37 Title: Antitermination extends the transcription unit Caption: An antitermination protein can act on RNA polymerase to enable it to read through a specific terminator.

Figure: 11-38 Title: Antiterminators can act at different locations in the transcription unit Caption: Host RNA polymerase transcribes lambda genes and terminates at t sites. pN allows it to read through terminators in the L and R1 units; pQ allows it to read through the R' terminator. The sites at which pN acts (nut) and at which pQ acts (qut) are located at different relative positions in the transcription units.

Figure: 11-39 Title: Termination is prevented by factors that act at nut Caption: Ancillary factors bind to RNA polymerase as it passes the nut site. They prevent rho from causing termination when the polymerase reaches the terminator.

대장균의 RNA중합효소

원핵생물의 Promoter Enhancer

RNA중합효소와 Promoter의 결합 Promoter : RNA중합효소가 특이적으로 결합하는 부위 시그마 소단위체 역할은 CPC - OPC로 전환 전사개시에 필수 Core enzyme Holoenzyme

시그마 재사용 회로

자연전사종결 (1)

자연전사종결 (2)

Rho-의존적 전사종결