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Cyclins and CDKs Cell Cycle Regulation
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- Опубликовано: 30 апр 2018
- A cell can switch from G0, or cell cycle arrest, to G1 once cells have attained a critical size. For multicellular organisms, growth factors and mitogens, which are substances encouraging cell division, need to be present. For unicellular organisms, nutrients must be adequate in surroundings. Once G1 is initiated, Cyclin D is synthesized and drives the G1/S phase transition.
In eukaryotes, Cyclin D binds with CDK 4 and CDK 6. These two complexes can partially phosphorylate retinoblastoma tumour suppressor protein, or Rb for short. Rb is bound to E2F, a transcription factor. When the CD-CDK4 and CD-CDK6 complexes partially phosphorylate Rb, it loosens its grip on E2F. E2F can then activate transcription of the cyclin E gene. Cyclin E binds CDK2, and this complex fully phosphorylates Rb, completing its inactivation.
Cyclin E also phosphorylates p27Kip1, an inhibitor of Cyclin D. Phosphorylation of p27Kip1 tags it for degradation. Degradation of this protein promotes expression of cyclin A. E2F also promotes transcription of cyclin A by removing the repressor molecule cell-cycle-responsive element (or CCRE) from the promotor, allowing the cell to enter S phase. The action of E2F on Cyclin A expression is part of a negative feedback loop, since the Cyclin A-CDK2 complex phosphorylates E2F, preventing it from removing the repressor molecule.
Cyclin A is the ONLY cyclin that plays a role in regulation of two cell cycle stages. It can activate two CDKs - CDK2 and CDK1. When Cyclin A forms a complex with CDK2, it allows the cell to progress to S phase. Meanwhile, binding of Cyclin A to CDK1 allows entry into M phase.
During S phase, Cyclin A resides in the nucleus. It directs the initiation and completion of DNA replication. Critically, Cyclin A ensures that DNA replication only occurs ONCE per cell cycle by preventing assembly of excessive replication complexes. How does it accomplish this?
Well, remember how Cyclin E is around at the end of G1? One way in which it helps the cell move into S phase is by initiating assembly of the pre-replication complex. This complex is needed for DNA replication to occur, and forms at the origin of replication. However, Cyclin A also associates with CDK2, and replaces Cyclin E. Once the Cyclin A-CDK2 complex concentration reaches a critical threshold, assembly of the pre-replication complex is terminated. The Cyclin A-CDK2 complex also regulates DNA replication by phosphorylating certain DNA replication machinery components.
Later in the S phase, Cyclin A also forms a complex with CDK1, remaining bound until late in the G2 phase, when it is replaced by cyclin B. The Cyclin A-CDK1 complex is believed to aid in activation and stabilization of the Cyclin B-CDK1 complex before being ubiquitinated. This degradation of the Cyclin A-CDK1 complex induces mitotic exit - in other words, the end of mitosis.
Cyclin B is a mitotic cyclin which binds to CDK1 to form the maturation promoting factor, or mitosis promoting factor - abbreviated MPF. The concentration of MPF rises until mitosis, until its concentration falls abruptly due to degradation of Cyclin B. High concentrations of Cyclin B are necessary for cells to enter M phase, and low concentrations are needed to exit M phase.
As a pharmacy student - who has a course in biology - I have to say,this is the best animated,well-explained and to the point video of explaining the subject of Cyclins and CDKs Cell Cycle Regulation ,it doesn't tire you at all and has all the necessary information for an in depth revision.I used this video when studying for my finals and it really helped.
as a chemistry-biology student, who has a science methods as a lesson - confirm
I'm also a pharmacy student and this vid has helped me lots.
This is the best video that I saw since the beginning of med school love you
for everybody who thinks this is complicated. THIS IS A PERFECT EASY EXPLANATION COMPARED TO PAPERS.
What papers? Where can i find them?
Swimming in my confusing notes and decided to come here. THIS is saving my grade right now in Graduate School! THANK YOU!
I was overwhelmed by the books but you made my life 100x easier! THANK YOU
People like you ,who make videos like this, deserve so much credit. Again, thank you so
Aww, thank you so much! ^_^
I will never forget Cyclins and CDKs because of your great visuals!
God bless you, I can't describe how much that helped me ❤❤
The animations are sooooo helpful. Also your voice tone is perfect. Thanks so much for sharing. Amazing job!!!!!!!
Thank you so much ^_^ You just made my day!!
This is the most amazing simple breakdown of this process I’ve ever seen thank you so much
how do lecturers expect us to memorise this bruh
Extremely Difficult explanation felt like she was reading out from a book. Dint understand a word! The words and vocabulary not easy to comprehend
Brilliant graphic concept, in this and other videos by the same author. Good texts, well researched, too.
Best description... It made me so clear about the concept...
It has a long chapter on the book but thankful that I watched this vid. I got a more simplified explanation.
This is AWESOME explanation I’ve ever seen
OH MY GOOD LORD. THIS IS SO FUCKING PRECIOUS. THANKS
The animations are perfect! thank you so much for this video, so helpful!!
This is one of the best videos i've ever seen, no doubt. Thanks a lot! ♥♥♥
First I want to thank you so much for this video! It was very well done! Also, I think it would be helpful if you were to insert the link to the video in which you discuss tumor suppressors at the time you mention it. Anyway, thank you again!
Perfect for the discussion of cell cycle checkpoints and regulation. truly of great help. Thanks!
WOW! that animation just makes it more fun and clear. The explanation so great Thank you very much
I'm so glad to have helped and made it fun! :-D
It is people like you, oh dear creators of this video, that help us science enthusiasts to get over the complicated topics! Thank you so much 🔥🔥🔥
In our books we use slightly different names for the cyclins, (like M-cyclin, S-cyklin, G1/S-cyclin etc.) was a bit confused at the start before realizing this
Wow superb please keep uploading videos. We are so thankful to you
thank you for all this efforts..was clear and helpful :)
Great breakdown! Great job!
Thank you so much ^_^
surely one of the best videos about this content!
Thank you so much!! ^_^
You saved my day
this is AMAZING thank you!
Amazing job! But i saw the entire video thrice and at 0.75x speed also had to pause alot. If there had been some gaps and the speed had been a little sow this would have been absolutely perfect.
Thanks for the feedback! :-) I will keep that in mind for future videos!
That's really so aspiring!
Thanks a zillion 😉
Hi, thank you for your great videos. My grandson has been diagnosed with CDKL5. Can you please do a video showing what happens when cyclins are deficient? Thanks again. :)
Thank you for this, because I have to write an essay on this tomorrow!
Needed this to help me understand what my cdk 4/6 inhibitor is doing. Lol
Thank you a great video 💕💕 well explained 👏👏
Thank you so much... i am sure this can't get easier than the way you explained.. Thank you again for providing free education
AWESOME! Thank you. Will definitely support you on patreon
excellent video thank you for your effort
i'll create another account so i can like this video twice
amaziiiing
this made so sense to me
THANKS I LOVE YOU FOR THIS
Extremely good. well done
Great video guys.
Helped a lot.
Thank you!
Wow what an amazing video! those pesky Cyclins always trying to get it their way >.
Amazing
Super clear thank you so much
I don't speak english😭😭😭😭😭😭
La vidéo a l'air tellement bien expliqué et animé
Oh! Pardon! Vous pouvez le traduire en cliquant sur CC au bas de la vidéo, puis en le traduisant automatiquement. J'espère que cela pourra aider! Bonjour du Canada :-)
@@NeuralAcademy Ah oui les sous-titres 😮 merci je n'y avais pas pensé 😁 Et bonjour de Guadeloupe
Great job 👏
Great effort 👍
excellent!!! thank you!
Cycline E : *Snaps*
P27 : Mr Stark, i don't feel so good
cringe
5:30 . Correction: The degradation of Cyclin A-CDK1 complex does not cause mitosis exit.
Deactivation of cyclin B-CDK1 complex causes the cell to exit mitosis.
Source of information: wikipedia
en.wikipedia.org/wiki/Cell_cycle#:~:text=transition).%5B28%5D%20Cyclin%20B%2Dcdk1%20complex%20activation%20causes%20breakdown%20of%20nuclear%20envelope%20and%20initiation%20of%20prophase%2C%20and%20subsequently%2C%20its%20deactivation%20causes%20the%20cell%20to%20exit%20mitosis.
Very hopeful thank you👌💜
Thank you very helpful!!!!!!!
thank you for this
I did not know p-53 was a Bulldog?
Of course it isn't literally... it's just a character to help with memorization!
Lmao
LOL, it"ll be a perfect name for my dog if I get one sometimes.
Thank you
saved my exAAMSSS
Isn´t P27 kip1 an inhibitor of cyclin E-CDK2, A-CDK2, ACDC2 and B-CDC2 and a stimulator for cyclin D-CDK4/6 ?
Have a goodnight everyone productions
Great video it really helped me but please for the future video give some time to process the information other than that u are gifted☺️☺️☺️
So is the S-phase triggered by the presence of Cyclin A or the removal of CCRE by E2F?
Heyy, then where did the cyclin D go if it doesn’t degrade?
Very good!! What is the class bibliography?
Thank you!!!!
The theatrics made it hard for me to follow, I think it's too busy. But people learn differently, so that's okay
my head is going to explode now
I LOVE YOU
amazing!!!!
Awesome
Haha, thank you! The animation is very cute.
Cdk can cause lipoma?
thankyou
I love you
I didn't know Sophie Turner teaches Cell Biology
Unfortunatly it was too fast to understand
Why is it important for CyclinA-CDK2 to inactivate E2F?
i guess so the procedure isnt starting again and again and again. So it is a control mechanism i would say.
So that there is only one cell cycle going at once..
It is just a tought though.
Great video! However, don't cyclin D1 concentrations decrease during S-phase and rebound during G2?
I don't know but this is so simple but too much for me to understand currently as i am 16 years old😀
Gibts das auch auf deutsch
this got me trippin
terlalu sangar
"multiply" 😢
bruh calm down talk slowly
There is a reason RUclips lets you change the playback speed. Maybe just use that instead of complaining in the comment section next time.
Dear Neural Academy
if i passed my exam and got 100 i'll give u an ice cream or something else. thanks
with love Jaluprms and fucker baqi29
Love the explanation, but the animations are SO distracting from the point of the lecture.
Ga paham
I feel like just listening to your video is enough, the visual aspect doesn't help, your doodles actually make understanding the content harder. Decent explanation tho.