timing from stochasticity
play

Timing from Stochasticity Scott Yang Nick Rhind (UMass Med) John - PowerPoint PPT Presentation

Modelling the Genome-wide Replication Program of Budding Yeast: Timing from Stochasticity Scott Yang Nick Rhind (UMass Med) John Bechhoefer (SFU) CMMT TGIF Series Dec 17, 2010 Take-home messages Should consider DNA replication from a


  1. Modelling the Genome-wide Replication Program of Budding Yeast: Timing from Stochasticity Scott Yang Nick Rhind (UMass Med) John Bechhoefer (SFU) CMMT TGIF Series Dec 17, 2010

  2. Take-home messages • Should consider DNA replication from a stochastic point of view • Precise timing of the replication program can emerge from stochasticity

  3. DNA replication http://www.paterson.man.ac.uk/cellcycle/replication.stm

  4. DNA replication: the Kinetics S phase S Non-replicated G1 Potential origins

  5. DNA replication: the Kinetics S phase S Non-replicated G1 Potential origins Origins + forks = replication program

  6. A Microarray Experiment synchronize Raghuraman et al . Science 2001

  7. Replication profiles Position x 100 % replication 0 Time (min) Raghuraman et al . Science 2001

  8. Replication profiles Replication time profile VI Raghuraman et al . Science 2001

  9. Replication profiles Position x Position x 100 100 % replication % replication 0 0 Time (min) Time (min) Raghuraman et al . Science 2001

  10. Replication profiles Replication time profile Replication fraction profile 100 VI % Replication 0 Raghuraman et al . Science 2001 McCune et al. Genetics 2008

  11. Point of Views More deterministic • Each origin has a preprogrammed firing time • plus some variation around that time

  12. Point of Views More deterministic More stochastic • Each origin has a • Each origin has a distribution of firing times preprogrammed firing time • has an expected firing • plus some variation around time that time

  13. Point of Views More deterministic More stochastic • Each origin has a • Each origin has a distribution of firing times preprogrammed firing time • has an expected firing • plus some variation around time that time • How to ensure precise firing • What counts the time and time if needed? how?

  14. Parametric model Firing-time distribution 0 100 200 Genome position (kb) x: origin position Cumulative firing-time distribution t 1/2 : median of distribution = sigmoid function t w : width of distribution v: globally constant fork velocity

  15. Parametric model Firing-time distribution 0 100 200 Genome position (kb) 100 x: origin position % rep. t 1/2 : median of distribution t w : width of distribution 0 v: globally constant fork velocity

  16. Key theoretical idea      N x x          i  f ( x , t ) 1 1 t   i     v    i 1 global fork velocity

  17. Result 1: fit McCune 2008

  18. Result 1: fit McCune 2008

  19. Result 2: firing-time distributions

  20. An idea Maybe…origins The number of MCM with wi th lot lots s of of exceeds the number MC MCM f M fire re of ORC by a factor of ear arly. y. 10 – 100 in various organisms! Nick Hyrien 2003

  21. Multiple stochastic initiators Firing-time dist. Time (min)

  22. Multiple initiator model Increasing # of initiators

  23. Point of Views More stochastic • How to ensure precise firing time if needed?

  24. Point of Views More stochastic • How to ensure precise firing time if needed? • Give it lots of MCM

  25. Point of Views More deterministic More stochastic • How to ensure precise firing • What counts the time and time if needed? how? • Give it lots of MCM

  26. Point of Views More deterministic More stochastic • How to ensure precise firing • What counts the time and time if needed? how? • Give it lots of MCM • ????

  27. Conclusions • DNA replication is a stochastic process • We have developed a flexible, analytical model • Timing needs not be from an explicit clock (contrary to most biologists’ intuitions?) • Timing can emerge from multiple stochastic initiators (MCM2 – 7) Yang, Rhind, Bechhoefer, MSB 2010

  28. Current work • Probe MCM occupancy and other factors • Other experimental setups & techniques • Other organisms  universal program? Molecular Systems Biology 6 :404 (2010) Thank you!

  29. Toy replication fraction profile A culture of cells T minutes into S phase 1 origin Average 100 % rep + + + + … 0 position Firing-time distribution

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend