Gene Transcription Regulation of Phage λ It utilizes two separate mechanisms to regulate early and late transcripts. Expression of early genes is regulated by the phage encoded N-protein that forms a termination-resistant RNAP complex.
How does lambda phage control transcription of its genome?
The lambda repressor is a self assembling dimer also known as the cI protein. It binds DNA in the helix-turn-helix binding motif. It regulates the transcription of the cI protein and the Cro protein. The life cycle of lambda phages is controlled by cI and Cro proteins.
How does lambda phage replicate?
Bacteriophage lambda can reproduce in two alternative modes of growth. In the lytic mode, the phage infects a bacterial cell, reproduces many copies of itself, lyses the host cell, and circulates through the environment to infect another host cell.
What 2 proteins control the lysogenic switch in lambda?
The two regulatory proteins cI (also known as ¬ repressor) and Cro , maintain this switch and the production of either determines the fate of the infected bacterium as increase in cI proteins promotes the lysogenic cycle whereas increase in Cro proteins promotes the lytic cycle.
What is retro regulation?
The int gene encodes the integrase that catalyzes integration (and excision) of l DNA to (or from) the Escherichia coli chromosome. The sib mutations destroy the RNase III recognition structure and stabilize the int mRNA, resulting in the increased synthesis of integrase; hence, this is referred to as retroregulation.
How is Lysogeny regulated?
The lysogenic pathway is governed by another immediate-early gene product, the CII protein. Once integrated, expression of the bacteriophage genes is repressed by CI protein, and the bacteriophage genome is replicated passively with the host chromosome.
How is the replication cycle of lambda phage different from that of T4?
How is the replication cycle of lambda phage different from that of T4? The genome of lambda phage can integrate in the bacterial genome and replicate in concert with the bacterial DNA. T4 can not do this but undergoes a replication cycle that results in cell lysis. The new properties are encoded in the phage DNA.
Why is lambda phage important in general cloning?
Lambda phage has been of major importance in the study of specialized transduction. Specialized transduction is the process by which a restricted set of bacterial genes are transferred to another bacterium. The genes that get transferred (donor genes) depend on where the phage genome is located on the chromosome.
Why is lambda phage called temperate phage?
Bacteriophage λ is a temperate phage, which, upon infection of Escherichia coli, enters either the lytic or lysogenic replication pathway. The latter is defined by the integration of the λ prophage within the bacterial host genome, where it is quiescently inherited by daughter cells.
Which are the two phage proteins required to maintain stable Lysogens?
Two phage proteins, Int and CI, are required to form stable lysogens. Int allows the integration of the phage genome into the bacterial chromosome, and CI represses the two early phage promoters to prevent any lytic phage gene expression.
How is the T4 phage different from the lambda phage quizlet?
How is the replication cycle of lambda phage different from that of T4? The genome of lambda phage can integrate in the bacterial genome and replicate in concert with the bacterial DNA. T4 can not do this but undergoes a replication cycle that results in cell lysis.
How does the lambda repressor work?
Lambda Repressor (Repressing Cro and Activating cI) Two dimers bind each at the OR1 and OR2 binding site located in PR [two dimers then interact to tetramerize] – when OR1 and OR2 are bound by the lambda repressors, the cro gene is repressed
What triggers the switch from lysogenic to lytic DNA damage?
Switch from Lysogenic to Lytic DNA damage triggers the switch – through RecA mediated proteolysis of lambda repressor – activated RecA not only cleaves the LexA but also the lambda repressor – lambda repressors bound at PR will get chewed up by the RecA as it gets activated when there is a damage in DNA
What is the role of promoter sequence in transcription?
Thus, the efficiency or strength of a promoter sequence serves to regulate transcription. Mutation of a single base in either the -10 sequence or the -35 sequence can diminish promoter activity. 14.
