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Questions and Answers
During which phase of the cell cycle does centriole disengagement typically occur, as regulated by Orc1 and Geminin function?
During which phase of the cell cycle does centriole disengagement typically occur, as regulated by Orc1 and Geminin function?
- S phase
- G1 phase (correct)
- M phase
- G2 phase
In eukaryotic DNA replication, what complex is essential for an origin to be used during the G1 phase?
In eukaryotic DNA replication, what complex is essential for an origin to be used during the G1 phase?
- DNA polymerase
- ORC (Origin Recognition Complex)
- preRC (pre-replicative complex) (correct)
- MCM helicase
Which of the following events is associated with the S phase of the cell cycle?
Which of the following events is associated with the S phase of the cell cycle?
- Centriole maturation
- Centriole disengagement
- Centriole separation
- Centriole elongation (correct)
In prokaryotic DNA replication, what is the role of DnaA protein at the origin of replication (oriC)?
In prokaryotic DNA replication, what is the role of DnaA protein at the origin of replication (oriC)?
How does Dam methylase activity influence the initiation of DNA replication in prokaryotes?
How does Dam methylase activity influence the initiation of DNA replication in prokaryotes?
Why is DNA methylation crucial in prokaryotic DNA replication licensing?
Why is DNA methylation crucial in prokaryotic DNA replication licensing?
Which structural feature is characteristic of prokaryotic replication origins to facilitate initial DNA strand separation?
Which structural feature is characteristic of prokaryotic replication origins to facilitate initial DNA strand separation?
Once DNA replication is complete, what must occur for the origins to become competent for initiation again?
Once DNA replication is complete, what must occur for the origins to become competent for initiation again?
What is the consequence of origin firing when CDK activity is high?
What is the consequence of origin firing when CDK activity is high?
What is the primary function of SeqA in prokaryotic DNA replication licensing?
What is the primary function of SeqA in prokaryotic DNA replication licensing?
In eukaryotic cells, what is the typical outcome of Cdk phosphorylation of pre-RC components during the S phase?
In eukaryotic cells, what is the typical outcome of Cdk phosphorylation of pre-RC components during the S phase?
What prevents additional preRC complex formation until the next G1 phase?
What prevents additional preRC complex formation until the next G1 phase?
How does the speed of DNA synthesis differ between prokaryotes and eukaryotes?
How does the speed of DNA synthesis differ between prokaryotes and eukaryotes?
What is the impact of using only one replication fork in eukaryotic chromosome replication?
What is the impact of using only one replication fork in eukaryotic chromosome replication?
According to the information, what are the components of the pre-replicative complex (preRC)?
According to the information, what are the components of the pre-replicative complex (preRC)?
Flashcards
ORC (Origin Recognition Complex)
ORC (Origin Recognition Complex)
A complex that binds to origins of replication in eukaryotes. It consists of several proteins and serves as a platform for the assembly of other proteins required for DNA replication.
Pre-Replicative Complex (pre-RC)
Pre-Replicative Complex (pre-RC)
The complex formed at replication origins in eukaryotes during the G1 phase of the cell cycle, consisting of the Origin Recognition Complex (ORC), MCM helicase, and other proteins.
Cyclin-Dependent Kinases (CDKs)
Cyclin-Dependent Kinases (CDKs)
Enzymes that regulate the cell cycle by phosphorylating target proteins, activity is dependent on binding to a cyclin regulatory subunit.
DNA Replication Licensing
DNA Replication Licensing
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Dam Methylase
Dam Methylase
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SeqA
SeqA
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Prokaryotic Replication Origins
Prokaryotic Replication Origins
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DnaA
DnaA
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DnaB Helicase
DnaB Helicase
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Study Notes
- DNA replication begins with initiation and DNA replication licensing
Prokaryotic Replication Origins
- These origins have a specific sequence necessary and sufficient to start replication
- The structure includes A=T-rich 13-mer repeats and DnaA 9-mer sites
Initiator Proteins (DnaA)
- They are DNA-binding proteins with specific sequences
- DnaA oligomerizes upon binding to the origin wrapped around an oligomer which facilitates open complex formation with HU
- DnaB helicase expands the replication bubble, and primase forms RNA primers
Methylation of Bacterial Origins
- Dam methylase adds methyl groups to "A" in 5'-GATC-3'
- This activity is dependent on the nutrient status of the cell, preventing premature initiation
- SeqA binds hemimethylated DNA, preventing DnaA from binding and ensures DNA is replicated once per division cycle licensing
Replication Rate
- Synthesis at the forks is about ~50 nt/sec in eukaryotes while ~500 nt/sec in prokaryotes
- Average size chromosomes need ~ 840 hours (35 days) with only 1 replication fork to replicate
- Origins are activated in clusters named replication units
Eukaryotic Origins (ARS)
- They're known as Autonomously Replication Sequences
- Not every eukaryotic origin is used in every S-phase
ORC: Origin Recognition Complex
- This complex has a ORC-binding site, unwinding region and an Abf1-binding site
Eukaryotic Origin Licensing
- Origins require a preRC complex to be assembled during the G1 phase, and is regulated by cyclin-dependent kinase (Cdk) activity
- The preRC is a pre-replicative complex composed of ORC + MCM helicase
- Pre-RCs form when Cyclin-dependent kinase (CDK) activity is low
- Origins 'fire' when CDK activity is high, however, preRC is not enough for this to occur
Role of Cyclin-Dependent Kinases (CDKs)
- The role of Cdks is to Regulate cell cycle transitions
- At the beginning of S-phase CDK phosphorylation of pre-RC activates firing of of the origin
- Cdks prevent any more preRC complexes to form until the next G1 phase.
- Each origin can fire only once per cell cycle.
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