„Transcription-Translation Feedback Loop“ – Versionsunterschied
| [ungesichtete Version] | [ungesichtete Version] |
General format of the page created |
Added information into introduction and general mechanisms |
||
| Zeile 2: | Zeile 2: | ||
<!-- EDIT BELOW THIS LINE --> |
<!-- EDIT BELOW THIS LINE --> |
||
= '''Transcriptional Translational Feedback Loop (TTFL)''' = |
= '''Transcriptional Translational Feedback Loop (TTFL)''' = |
||
'''Transcription-translation feedback loop (TTFL)''', is a cellular model for explaining [[Circadian rhythm|circadian rhythms]] in behavior and [[physiology]]. Widely conserved across species, the TTFL is auto-regulatory, in which transcription of clock genes is regulated by their own protein products. |
|||
== Discovery == |
|||
Beginning in 1729, French astronomer [[Jean-Jacques d'Ortous de Mairan|Jean-Jacques d’Ortous de Mairan]]’s observed periodic 24-hour movement of mimosa pant leaves. Though [[Circadian rhythm|circadian rhythms]] have been documented for centuries, science has only recently begun to uncover the cellular mechanisms responsible for driving observed circadian rhythms. The cellular basis of circadian rhythms is supported by the fact that rhythms have been observed in [[Unicellular organism|single-celled organisms]] <ref>{{Citation|last=Johnson|first=Carl Hirschie|title=Circadian Rhythms in Unicellular Organisms|date=2001|url=https://doi.org/10.1007/978-1-4615-1201-1_4|work=Circadian Clocks|pages=61–77|editor-last=Takahashi|editor-first=Joseph S.|series=Handbook of Behavioral Neurobiology|publisher=Springer US|language=en|doi=10.1007/978-1-4615-1201-1_4|isbn=9781461512011|access-date=2019-04-10|last2=Kondo|first2=Takao|editor2-last=Turek|editor2-first=Fred W.|editor3-last=Moore|editor3-first=Robert Y.}}</ref> |
|||
<br /> |
|||
Beginning in the 1970s, experiments involving [[Forward genetics|forward genetic methods]], conducted by [[Ronald J. Konopka|Ron Konopka]] and colleagues, revealed that ''Drosophila melanogaster'' specimens with altered ''period'' (''Per'') genes also demonstrated altered periodicity. As genetic and molecular biology experimental tools improved, researchers further identified genes involved in sustaining normal rhythmic behavior, giving rise to the concept that internal rhythms are modified by a small subset of ‘core clock genes’. Hardin and colleagues (1990) were the first to propose that the mechanism driving these rhythms were a negative feedback loop, giving rise to the transcription-translation feedback loop (TTFL) model that has now become the dominant paradigm for explaining circadian behavior in both plants and animals.<ref>{{Cite web|url=https://www.sciencedirect.com/science/article/pii/S2213020915000294|title=A brief history of circadian time: The emergence of redox oscillations as a novel component of biological rhythms|last=Wulund|first=Lisa|last2=Reddy|first2=Akhilesh B.|date=|website=www.sciencedirect.com|archive-url=|archive-date=|dead-url=|access-date=2019-04-10}}</ref> |
|||
=== Discovery === |
|||
<br /> |
|||
== General Mechanisms of TTFL == |
|||
The TTFL is a [[Negative feedback|negative feedback loop]], in which clock genes are regulated by their protein products. Generally, the TTFL involves positive regulatory elements that promote transcription and protein products that suppress transcription. When a positive regulatory element binds to a clock gene promoter, transcription proceeds, resulting in the creation of an mRNA transcript and, after translation, a protein product. There are characteristic delays between mRNA transcript accumulation, protein accumulation, and gene suppression due to translation dynamics, post-translational protein modification, the protein dimerization, and intracellular travel to the nucleus. Once enough modified protein accumulates in the cytoplasm, protein products are transported into the nucleus where they remove the positive element from the promoter to stop<br /> |
|||
<br /> |
|||
== Prominent Models == |
|||
=== Mammals === |
|||
=== Drosophila === |
|||
=== Cyanobacteria === |
|||
=== Plants === |
|||
=== Fungi === |
|||
Version vom 10. April 2019, 06:27 Uhr
Transcriptional Translational Feedback Loop (TTFL)
Transcription-translation feedback loop (TTFL), is a cellular model for explaining circadian rhythms in behavior and physiology. Widely conserved across species, the TTFL is auto-regulatory, in which transcription of clock genes is regulated by their own protein products.
Discovery
Beginning in 1729, French astronomer Jean-Jacques d’Ortous de Mairan’s observed periodic 24-hour movement of mimosa pant leaves. Though circadian rhythms have been documented for centuries, science has only recently begun to uncover the cellular mechanisms responsible for driving observed circadian rhythms. The cellular basis of circadian rhythms is supported by the fact that rhythms have been observed in single-celled organisms [1]
Beginning in the 1970s, experiments involving forward genetic methods, conducted by Ron Konopka and colleagues, revealed that Drosophila melanogaster specimens with altered period (Per) genes also demonstrated altered periodicity. As genetic and molecular biology experimental tools improved, researchers further identified genes involved in sustaining normal rhythmic behavior, giving rise to the concept that internal rhythms are modified by a small subset of ‘core clock genes’. Hardin and colleagues (1990) were the first to propose that the mechanism driving these rhythms were a negative feedback loop, giving rise to the transcription-translation feedback loop (TTFL) model that has now become the dominant paradigm for explaining circadian behavior in both plants and animals.[2]
General Mechanisms of TTFL
The TTFL is a negative feedback loop, in which clock genes are regulated by their protein products. Generally, the TTFL involves positive regulatory elements that promote transcription and protein products that suppress transcription. When a positive regulatory element binds to a clock gene promoter, transcription proceeds, resulting in the creation of an mRNA transcript and, after translation, a protein product. There are characteristic delays between mRNA transcript accumulation, protein accumulation, and gene suppression due to translation dynamics, post-translational protein modification, the protein dimerization, and intracellular travel to the nucleus. Once enough modified protein accumulates in the cytoplasm, protein products are transported into the nucleus where they remove the positive element from the promoter to stop
Prominent Models
Mammals
Drosophila
Cyanobacteria
Plants
Fungi
- ↑ Vorlage:Citation
- ↑ Lisa Wulund, Akhilesh B. Reddy: A brief history of circadian time: The emergence of redox oscillations as a novel component of biological rhythms. In: www.sciencedirect.com. Abgerufen am 10. April 2019.