Greatwall

New Co-Author Publication! Ensa controls S-phase length by modulating Treslin levels.

Posted on

Great news, we have published a co-authored paper entitled ‘Ensa controls S-phase length by modulating Treslin levels’ in the prestigious journal ‘Nature Communications’. This work was started back in 2011 when I was a Post-Doc in the laboratory of Anna Castro in France. It’s exciting to see those inital discoveries transition into the finished paper.
The article is Open Access and free to download, which you can do so here: http://www.nature.com/articles/s41467-017-00339-4

 

ABSTRACT

The Greatwall/Ensa/PP2A-B55 pathway is essential for controlling mitotic substrate phos- phorylation and mitotic entry. Here, we investigate the effect of the knockdown of the Gwl substrate, Ensa, in human cells. Unexpectedly, Ensa knockdown promotes a dramatic extension of S phase associated with a lowered density of replication forks. Notably, Ensa depletion results in a decrease of Treslin levels, a pivotal protein for the firing of replication origins. Accordingly, the extended S phase in Ensa-depleted cells is completely rescued by the overexpression of Treslin. Our data herein reveal a new mechanism by which normal cells regulate S-phase duration by controlling the ubiquitin-proteasome degradation of Treslin in a Gwl/Ensa-dependent pathway.

Advertisements

Switching off Cancers Diversity

Posted on

JCS paper

A defining feature in over 2/3rds of all solid tumours is the continual loss and gain of whole are small parts of chromosomes. This instability, or CIN for short, strongly implicated in tumour initiation, progression, chemoresistance and poor prognosis. CIN is created through failures during mitosis, whereby whole or parts of a chromosome are segregated incorrectly, thereby created daughter cells with unequal chromosome numbers. Consequently, understanding how mitosis is regulated is essential for uncovering the mechanisms allowing CIN to arise and drive cancer. In our recent publication, we discovered the mechanisms controlling the key regulatory pathway critical to ensuring cells exit mitosis correctly. At the centre of this pathway is a gene call MASTL (short for ‘Microtubule Associated Serine/Threonine Kinase-Like’). The primary function of MASTL is to ensure that the cellular breaks (the phosphatase PP2A), is turned off during mitosis so that the accelerator (Cdk1 kinase) can drive the cell into mitosis. Much like a car, having the accelerator and breaks on at the same time is a bad idea, unless you like the smell of burning rubber. To successfully exit mitosis, and to perfectly segregate chromosomes, the cell must take the foot off the accelerator and turn on the breaks. Because MASTL is the central regulator ensuring the breaks are coordinated with the accelerator, it is essential to understand how MASTL is controlled. To this end, we uncovered that MASTL must be rapidly turned off to allow cells to exit mitosis, and this inactivation is carried out by another cellular brake call PP1 phosphatase (Rogers et al, JCS 2016). Now that we have identified and mapped this novel mitotic exit switch, we hope to be able to shed new light on how CIN drives the initiation and evolution cancer. We believe that with further study we will be able to better predict patient response to chemotherapy, and also identify new ways to ‘switch off’ highly unstable tumours, thereby improving treatment for patients that currently have a very poor prognosis.

Image of Interphase HeLa cell stained for Actin (red), DNA (blue) and the co-localisation of MASTL and PP1 by Proximity Ligation Assay (PLA; green).
Credit: Sam Rogers and Cell Division Lab

 

Were the front cover feature image on this months issue of Cell Cycle !

Posted on Updated on

Some more good news to coincide with today’s official release of our manuscript, one of our images has been chosen to be the feature image on the front cover.

It’s a great honour, one that I am very proud of, and is the first time I have ever had a front cover !
You can view the current issue (Volume 13 – Issue 9 – May 1, 2014) here.

Or jump directly to our paper here

Front Cover 

FrontCoverCC13-9

 

Read the rest of this entry »

A brief Intro to Greatwall Kinase…The King of Mitosis

Posted on Updated on

Our favourite protein in the lab is Greatwall kinase. It was first discovered in 2004 to be critical for cell division in fruit flies (1,2) . The trail then went cold for a few years as to its exact function, but in 2009, while I was working as a post-doc in France, I was fortunate enough to be in the lab that uncovered its exciting mode of action. For cells to get into mitosis they must activate a key protein called cyclin dependent kinase 1 (Cdk1). I like to think of this as the accelerator in a car. So to get moving cells push on the gas!
And conversely to get out of mitosis you need to hit the brakes. These brakes are the phosphatases which reverse the action of kinases like Cdk1. That’s great but what is missing from this equation?
Well like any car it’s pretty useless without a driver to co-ordinate the accelerator and brakes. And this is where Greatwall (Gwl for short) comes in. It makes sure that when Cdk1 (accelerator) turns on that the breaks get turned off and vice versa (3,4). Without Gwl the cell gets into a lot of trouble very fast, which you can see in the image below. Here I depleted the human version of Gwl (a gene called MASTL) and watched what happened as cells tried to undergo mitosis (5). As you can see they don’t do a very good job… the result is cells fail to divide correctly, resulting in multiple defects and often cell death.

Gwl Figure

I hope you enjoyed part one of my feature on Gwl, and in part 2 I will into more details about this amazing and exciting new protein.

References:

1. Bettencourt-Dias, M. et al. Genome-wide survey of protein kinases required for cell cycle progression. Nature 432, 980–987 (2004).

2. Yu, J. et al. Greatwall kinase: a nuclear protein required for proper chromosome condensation and mitotic progression in Drosophila. J Cell Biol 164, 487–492 (2004). [Link]

3. Vigneron, S. et al. Greatwall maintains mitosis through regulation of PP2A. EMBO J 28, 2786–2793 (2009). [Link]

4. Lorca, T. et al. Constant regulation of both the MPF amplification loop and the Greatwall-PP2A pathway is required for metaphase II arrest and correct entry into the first embryonic cell cycle. J Cell Sci 123, 2281–2291 (2010). [Link]

5. Burgess, A. et al. Loss of human Greatwall results in G2 arrest and multiple mitotic defects due to deregulation of the cyclin B-Cdc2/PP2A balance. Proc Natl Acad Sci USA 107, 12564–12569 (2010). [Link]