Protein complex clears potential traffic jams in RNA production, finds research

Agencies
April 6, 2019

April 6: A new research has found that a protein complex plays a key role in clearing potential traffic jams in the production of RNA.

The research was published in the journal Genes & Development.

"The 'Ccr4-Not' complex is involved in nearly every step of this process from start to finish. Our new research shows that this complex has an additional function that helps maintain normal cellular function when something goes wrong during transcription," said Joseph C. Reese, a researcher.

During the transcription of RNA from DNA, RNAPII, itself a large complex made up of multiple protein subunits, travels along the strand of DNA reading the ATCG sequence and producing a complementary strand of RNA.

If the RNAPII encounters DNA damage, which can be caused by UV radiation and other sources, it can become stuck and prevent trailing polymerases from completing transcription of the gene, similar to how a stalled car prevents traffic behind it from flowing.

If this jam cannot be cleared, multiple RNAPIIs transcribing the same gene can start to pile up in a sort of traffic jam preventing the DNA from being repaired and hampering cell function.

"Defects in this pathway have been associated with a number of diseases and human syndromes, such as Cockayne syndrome- a neurodegenerative disorder that results in growth failure, neurological developmental defects, and sensitivity to UV light," Reese added.

RNA polymerase II (RNAPII), the enzyme that produces RNA from a DNA template, can become stuck due to damage to the DNA template, and these jams must be cleared to restore gene expression and normal cell function.

New research shows that the master regulatory complex, 'Ccr4-Not' performs this task, associating with RNAPII during the transcription of RNA from DNA and marking RNAPII for degradation when it becomes stuck, allowing the DNA to be repaired and normal cell function to resume.

"Normal cellular functions rely on what is sometimes called the 'central dogma of biology,'" said Reese.

The researchers used genetic methods and reconstitution biochemistry- a method whereby purified components of a cellular process can be added- taken away, and mixed in a precisely controlled manner to identify exactly how they function to show that 'Ccr4-Not' recruits factors that mark RNAPII with a small signalling molecule called ubiquitin.Attachment of ubiquitin to RNAPII triggers other cellular components to degrade the enzyme, clearing the jam.

"Mutating members of the 'Ccr4-Not' complex makes cells more sensitive to agents that damage the genome, but because 'Ccr4-Not' is involved in so many aspects of gene regulation it wasn't clear until now what its precise role was," said Reese.

"The fact that 'Ccr4-Not' recruited the destruction machinery to RNAPII was a surprising result, and suggests it acts as a tow truck to remove traffic jams throughout the genome," he added.

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Agencies
June 20,2020

The World Health Organisation has warned that the COVID-19 pandemic is entering a "new and dangerous" phase. Thursday saw the most cases in a single day reported to the WHO.

Tedros Adhanom Ghebreyesus said the day had seen 150,000 new cases with half of those coming from the Americas and large numbers also from the Middle East and South Asia, the BBC reported.

He said the virus was still spreading fast and the pandemic accelerating.

He acknowledged people might be fed up with self-isolating and countries were eager to open their economies but he said that now was a time for extreme vigilance.

Maria van Kerkhove, technical lead of the WHO's COVID-19 response, told a press conference the pandemic is "accelerating in many parts of the world".

"While we have seen countries have some success in suppressing transmission and bringing transition down to a low level, every country must remain ready," she said.

Mike Ryan, the head of the WHO's Health Emergencies Programme, said that some countries had managed to flatten the peak of infections without bringing them down to a very low level.

"You can see a situation in some countries where they could get a second peak now, because the disease has not been brought under control," he said.

"The disease will then go away and reduce to a low level, and they could then get a second wave again in the autumn or later in the year."

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Agencies
April 4,2020

Washington D.C., Apr 4: While consuming a high-diet salt can result in high blood pressure, a recent study has revealed a link between salt-rich diet and weaker immune system.

The study was conducted under the leadership of the University Hospital Bonn, and the results were published in the journal Science Translational Medicine.

The research was conducted on mice that were fed a high-salt diet. Later, they were found to suffer from much more severe bacterial infections.

Human volunteers who consumed an additional six grams of salt per day also showed pronounced immune deficiencies.

The World Health Organization (WHO) has recommended a maximum amount of five grams of salt a day.

It corresponds approximately to one level teaspoon. In reality, however, many Germans exceed this limit considerably. 

Figures from the Robert Koch Institute suggest that on average men consume ten, and women more than eight grams a day.

This means that we reach for the salt shaker much more than is good for us. After all, sodium chloride, which is its chemical name, raises blood pressure and thereby increases the risk of heart attack or stroke.

"We have now been able to prove for the first time that excessive salt intake also significantly weakens an important arm of the immune system," said Prof. Dr. Christian Kurts from the Institute of Experimental Immunology at the University of Bonn.

This finding is unexpected, as some studies point in the opposite direction. For example, infections with certain skin parasites in laboratory animals heal significantly faster if these consume a high-salt diet.

The study also sheds light on the fact that the skin serves as a salt reservoir.

"Our results show that this generalization is not accurate," emphasized Katarzyna Jobin, lead author of the study.

The body keeps the salt concentration in the blood and in the various organs largely constant. Otherwise important biological processes would be impaired. The only major exception is the skin which functions as a salt reservoir of the body. This is why the additional intake of sodium chloride works so well for some skin diseases.

However, other parts of the body are not exposed to the additional salt consumed with food. Instead, it is filtered out by the kidneys and excreted in the urine.

"We examined volunteers who consumed six grams of salt in addition to their daily intake," said Prof. Kurts. This is roughly the amount contained in two fast-food meals, i.e. two burgers and two portions of French fries.

After one week, from the results, it showed that the immune cells coped much worse with bacteria after the test subjects had started to eat a high-salt diet.

In human volunteers, excessive salt intake also resulted in increased glucocorticoid levels.

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