ECRs at ICaMB: RNA Quality Control


Claudia SchneiderIn the latest of our series focussing on the ECRs in ICaMB, we feature Dr Claudia Schneider. Claudia obtained her PhD from the Philipps-University in Marburg, Germany. She then moved to the UK to work with Prof David Tollervey at the Wellcome Trust Centre for Cell Biology in Edinburgh. In 2011, she was awarded a Royal Society University Research Fellowship and started her own lab at ICaMB. Here, Claudia describes her research, and how being alarmed during her postgraduate studies triggered her long-term research interest.

By Dr Claudia Schneider

Hi, my name is Claudia Schneider, and my Royal Society University Research Fellowship has allowed me to set up my own group here at ICaMB to study enzymes involved in RNA processing and quality control.

I am originally from Germany, where I did my undergraduate studies and my PhD. Many people might think that Germany is the land of cars or lederhosen – but in truth it is really the land of bread (and beer!). It might therefore not come as a surprise that baker’s yeast has become my favourite model organism.

Click on the image to find out how to make these budding buns!

Click on the image to find out how to make these budding buns!

During my undergraduate studies I was first introduced to RNA and I was (and am still) amazed by its many known and still emerging functions in the cell. We now know that almost the entire eukaryotic genome is transcribed, but only a small fraction of the transcripts are protein-coding messenger RNAs (mRNAs). The others are stable and unstable non-coding RNAs (ncRNAs), which are involved in all aspects of gene expression. RNA molecules are often extensively processed before they’re functional, and each processing step is subject to quality control mechanisms. If you want to know more about the life and death of non-coding RNAs, have a look at this recent review.

Yeast has not always been my first choice to study RNA metabolism, since the object of my PhD project in Prof Reinhard Lührmann’s lab turned out to be completely missing in baker’s yeast. Back then I worked on nuclear pre-mRNA splicing, the removal of non-coding introns from precursor mRNAs catalysed by the spliceosome. It was an exciting time in the splicing field: A second low abundance “minor” spliceosome had just been discovered in most multicellular eukaryotes (with the strange and still not readily explainable exception of C. elegans), and this complex is not present in yeast. The minor spliceosome recognises a rare class of introns (<0.5%) with different consensus sequences at the splice sites and has since been linked to a number of human diseases. During my PhD, I purified and biochemically characterised the snRNP components of this unusual pre-mRNA splicing machinery in human and Drosophila cells.

Since then, I have been fascinated by biochemical and enzymatic assays involving RNA such as in vitro splicing assays, where in vitro transcribed pre-mRNAs are mixed with purified spliceosomes. The goal of such an experiment is to observe precise and (hopefully) pretty intron removal in the test tube – but, to my great annoyance, success was every so often hampered by a powerful ribonuclease (RNase) contamination in the assay that completely trashed the precious RNA substrates. Generic and aggressive RNases like RNase A are found on our skin, are incredibly stable and can even survive boiling.

Common decoration on lab surfaces during my PhD

Common decoration on lab surfaces during my PhD

It is therefore fair to say that my scientific career was majorly influenced by constant warnings by my mentor, who told me that all RNases are evil and must be destroyed. However, for my postdoc, I decided to face my fears and look these evil RNases in the eye, in the humble model system yeast. During my time with Prof David Tollervey at the University of Edinburgh, I learned that there are many different types of RNases, and only very few of them are promiscuous and chop RNA to bits.

The majority of RNases are very sophisticated and versatile enzymes. Several RNases are capable of degrading only specific RNA molecules, or only function under certain circumstances, and protein co-factors often assist in substrate recognition. RNases are crucial elements in RNA quality control or surveillance systems, which distinguish aberrant from “normal” RNA molecules. One clinically important RNA surveillance pathway is called “nonsense-mediated decay” or NMD, and this system recognises and degrades a specific class of defective mRNAs to limit the synthesis of truncated and potentially toxic proteins. NMD defects are linked to ~30% of all inherited human diseases (e.g. Duchenne muscular dystrophy and forms of b-thalassemia) as well as certain types of cancer. In addition to quality control/surveillance, where RNAs are mostly completely degraded, a growing number of RNases have been shown to be responsible for precise processing or “trimming” of precursor RNA molecules to produce their functional forms.

Exonucleases were long believed to be the main players involved in RNA recognition and processing/turnover. However, this model was recently challenged by the identification of endonucleases containing PIN (PilT N-terminus) domains, which appear to play key roles in RNA metabolism. Eight PIN domain proteins and therefore putative endonucleases are encoded in the genome of budding yeast, and this includes three largely uncharacterised “orphan” nucleases.

Overall it is still puzzling to me how individual RNases “make the decision” to either completely degrade or carefully process a specific RNA. Given the ever-growing number of non-coding transcripts in the cell, I am also keen to know which RNases are responsible for which substrates and what the so-far uncharacterised putative PIN domain endonucleases in yeast are doing!

To this end, our lab is using an RNA-protein cross-linking method called “CRAC” (UV cross-linking and analysis of cDNA) to identify the targets of PIN domain endonucleases on a transcriptome-wide scale. The CRAC method and the machinery to cross-link yeast cultures were developed by Sander Granneman at the University of Edinburgh, when we were both PostDocs in Prof David Tollervey’s lab. Sander now has his own lab too, and he runs a CRAC-blog. Interestingly, the cross-linking device we are using was originally designed to sterilise sewage water, but it is now also commercially available for research. With this setup, yeast cells are cross-linked while they are growing in culture, which is crucial to identify the often very transient interactions between nucleases and their target RNAs. This system provides a huge advantage over more traditional cross-linkers like the “Stratalinker”, which requires pelleting and cooling the cells on ice before cross-linking. It is, however, also much bigger and takes up a whole bench in the lab – but I guess there is a drawback to everything! In any case: if you want to find RNA targets for your favourite yeast protein – get in touch!!

Cultures of Saccharomyces cerevisiae can be “zapped”, while they are growing: It only takes 100 seconds!

Cultures of Saccharomyces cerevisiae can be “zapped”, while they are growing: It only takes 100 seconds!

Transcriptome-wide RNA-protein interaction analyses generate huge datasets and we use RNA binding and nuclease assays, as well as co-precipitation studies, to validate the in vivo cross-linking results for individual PIN domain endonucleases.

With the help of an ERASMUS exchange student, Franziska Weichmann, who spent 6 months in my lab last year, we have made good progress with two putative PIN domain endonucleases that are linked to ribosome biogenesis. We were able to identify their binding sites on the pre-ribosomal RNAs, as well as co-factors that are important to recruit them into the pre-ribosome. We have also set up an in vitro system with recombinant proteins, and we are currently trying to convince one of them to specifically cleave its proposed rRNA substrate in the test tube – and we are slowly getting there…..

Like the other ICaMB ECRs, who posted on this Blog before, I would like to finish by saying that having my own lab has been an exciting and (on most days) enjoyable adventure so far – and I am looking forward to the next set of challenges…

Antisense Science: A Science Blog by Students


Blogs are now a widespread science communication tool, with many researchers taking to the blogosphere to discuss the latest scientific discoveries, explain the basic concepts in their research field to a wide audience or just talk about science and scientists. Our 3rd year bioscience students have done just that, and this week we have a guest post prepared by them.


by Antisense Science

Antisense Science is a science blog founded by a group of 3rd year bio-scientists from Newcastle University. As a team, we recognise that science is not as accessible to the general public as it should be.  We therefore make it our primary aim to translate complex scientific principles and research articles that interest us personally, into topical, thought provoking blogs accessible to everyone.

Our project is small but our ambition is big! Since our founding in October 2013 we have published 58 articles covering psychoactive baths salts, human evolution and the neurobiology of love, to name a few, and with a growing following (we’ve had over 6000 hits since inception) we were thrilled to be given the opportunity to guest post on ICaMBlog. As Newcastle University students, our interest in research was stirred by the professors at Newcastle University, including those who founded this blog. With planned guest posts focusing on research by Prof Rick Lewis among others, maybe YOU will feature on Antisense Science in the near future! We foresee (we hope!) that our blog can form a bridge between researchers here at Newcastle and the student body, raising awareness of what is actually being discovered right under our noses. By forming mutually beneficial collaborations, we hope to diversify and grow our following and expose our current readers to a continual stream of stimulating articles which never fail to pique the interest of the curious.

Meet the Antisense Science team

Meet the Antisense Science team

Currently, we have a total of 7 writers, all of whom enjoy sharing the intrigue of the latest developments in science, from biochemistry to microbiology (and even physics) and we have no plans of stopping. Although many of us will be moving on from our BScs to ever greater things, Antisense Science will remain and we are even in the process of recruiting further up and coming bio-scientists as writers (keep your eyes peeled for blogs from first year students Bethany Lumborg and Lucy Gee, as well as our fellow third year Emily Lawson and a multitude of guest posters from across the student body). The future looks bright and we’re very glad with the progress we have made thus far!

For an example of what we do, here is an article on depression written by our very own Joe Sheppard. We hope you enjoy it!  If you ever want to be involved in any of our projects feel free to drop us a message.  We also have Facebook ( and Twitter (@AntisenseSci) so there are plenty of ways to keep in the loop.


The Confounding Contradictions of Depression

If you currently have or have had depression then you may already be able to tell your MAOIs from your SSRIs, but if you haven’t then what you read here might actually help. Knowledge is power and I believe learning a little something about depression could contribute a bit of control to an otherwise daunting and often underestimated medical condition.

Depression is perhaps the ultimate “common complex disorder”. Unlike pathogens or mutations that affect physical body tissue, depression is a condition that alters the very consciousness and emotional state of an individual making it a truly unique affliction. Throughout the course of our lives 1 in 5 of us will experience depression or anxiety of some kind, yet the majority of people conceive depression  simply as a disease of “sadness” when the truth is much more complex. “Anhedonia“, an inability to feel joy in anything and “congruent memory bias”, the inability to remember or altered recall of specific memories, are extremely common cognitive behaviours in depression that we often inflict upon ourselves on a day to day basis.

It may surprise you to know that modern science can say with little certainty what neuro-physiological changes initiate depression, and linking those that we do think are involved to the broad psychiatric manifestations seen in cases of depression is even harder as human experience and consciousness is beyond the understanding of molecular neuroscience (and by extension, definitely me). But from the murky depths of our own minds patterns do emerge, and as such there are a few good theories out there.

Rather confusingly the best fitting theory of depression is actually based on the drugs WE ALREADY USE to treat it, not a common theme in medicine, I might add. “The monoamine theory of depression” states that depressed brains have reduced signalling between neurons via a group of specific chemical neurotransmitters called monoamines. Two in particular called 5-hydroxytryptophan (hereafter referred to as serotonin) and dopamine are released into a synapse to induce electrical signals between neurons in the midbrain. These two neurotransmitters and the resulting electrical signals are most notably perceived as feelings of joy, euphoria, reward and attention. And there is some evidence to back this up: depletion of tryptophan, an amino acid essential for serotonin synthesis in the brain, caused mood congruent memory bias, and altered reward-related behaviours. Biochemical evidence exists too, abnormalities of the protein that binds serotonin in the brain called the 1A receptor have been noted in multiple brain areas of major depressive disorder (MDD) patients. Why does serotonin decline in patients with depression? Well, search my pockets, you will find no answers.

Rather reassuringly this hasn’t stopped treatment of depression at all, and several drugs for which the theory is named are all targeted at increasing serotonin, and so good feelings, within the brain. The so named selective serotonin re-uptake inhibitors (those “SSRIs” I snuck in earlier, such as fluoxetine and sertraline) are the most prescribed group of antidepressants and work in a way best aided pictographically:


Schematic representation of neuron activity

Serotonin is synthesised in the presynaptic neuron from tryptophan, from here it is packaged into vesicles and upon nerve impulse firing (see previous article “ shedding light on neural networks”) is released in the synaptic cleft (the space between neurons).  Serotonin then binds to receptors on the postsynaptic neuron, stimulating a similar nerve impulse. However, serotonin is also able to control its own release: By binding to the 1A receptor on the presynaptic neuron it prevents continued release of serotonin, allowing the proposed channel protein SCL6A4 to re-absorb serotonin in the presynaptic neuron to be destroyed.

This is where SSRIs come in. Believed to bind to SCL6A4 and prevent the re-absorption of serotonin, it allows serotonin to remain in the synaptic cleft for longer and therefore stimulate nerve impulses in the post synaptic neuron for longer, and so increase the degree of monoamine signalling.

Let’s not forget our friend dopamine:

Dopamine too is a monoamine consistently found reduced in the blood of patients with depression, as a result of decreased synthesis and degradation in the brains of these patients. Neurons that signal using dopamine (as opposed to serotonin) are found in a region of the brain called the substantia nigra that degenerates during Parkinson’s disease. Interestingly the motor impairment (shaking) in this disease is often preceeded by major depressive disorder in 50% of Parkinson’s cases!

This brings me quite nicely to my final point. Since so little is known about the basis of psychiatric disorders their treatment has been almost purely symptomatic for the last 60 years. Thomas Insel, director of the US National Institute for Mental Health was quoted in 2013 as saying “In the rest of medicine, this would be equivalent to creating diagnostic systems based on the nature of chest pain, or the quality of fever.” This was following the release of the 5th edition of the diagnostic and statistical manual of mental disorders (DSM-5), that diagnoses psychiatric conditions based on common symptoms presented by each condition. Despite the strong agreement with Insel by many psychiatrists that this method is outdated, the shift to a more objective and molecular diagnostic is years away given the outstanding complexity of these diseases. But keep the hope, recent booms in neuroscience research are a sure step towards a less archaic means of treating depression and other mental disorders.

A new approach spearheaded by the same Thomas Insel called “Research Domain Criteria” or RDoC is already doing just that by utilizing genomic sequencing technology, fMRI imaging techniques and cognitive science to develop an entirely new platform for diagnosis based on new data being attained all the time, rather than the laboured DSM-5 classification. While still in its infancy this new approach aims to start looking at broader groups for diagnosis rather than classification of different disorders by the symptoms they present. For instance, by looking at a group of patients with different disorders but all experiencing anhedonia will not only allow a greater insight into a unifying cause for these symptoms, but also speed up treatments in the future.

Of course, there are always two sides to each argument and depression does in some sense stand alone from other psychiatric disorders such as schizophrenia in that it imparts a greater emotional influence on the sufferer – if “precision medicine” were able to prescribe a pill for the treatment of emotional conditions, would you want it to? Of course this is a quandary we won’t face for some time, but worth a thought.


Some interesting but by no means comprehensive reviews on depression, its far too huge for 3 articles!

Hasler G (2010). Pathophysiology of depression: do we have any solid evidence of interest to clinicians? World psychiatry : official journal of the World Psychiatric Association (WPA), 9 (3), 155-61 PMID: 20975857

Martinowich K, Manji H, & Lu B (2007). New insights into BDNF function in depression and anxiety. Nature neuroscience, 10 (9), 1089-93 PMID: 17726474

Frances, A. (2013) One manual shouldn’t dictate US mental health research
(Accessed: 07/01/14).