CUT60 — don’t cut the junk
Non-coding RNA sequences are important to keep the powerhouse of a cell intact
Genes are made up of DNA and contain the information to make proteins, which carry out a variety of roles in the cell and the body. First, the information found on DNA needs to be transcribed into RNA molecules, which then act as a template to build the actual proteins. However, the vast majority of DNA does not encode proteins. Nevertheless, these non-coding regions of DNA (often given the popular but misleading name ‘junk-DNA’) are still transcribed into non-coding RNA. The purpose of this type of RNA is largely unclear, although some are known to activate certain genes. The transcription of non-coding RNA is also sensitive to environmental changes, suggesting it may play other important roles in the cell.
Not all DNA — including non-coding DNA– is copied into RNA in one go. Usually, every DNA sequence is transcribed separately as one unit. These units have clearly marked start and end points. If these marker points are overridden the transcription process can overlap onto the next sequence.Thus, in the case of coding DNA, proteins may not form properly. However, until now it was unclear if missed marker points in non-coding RNA may also have consequences.
To investigate this further, du Mee et al. mutated several non-coding parts of the DNA in yeast. The experiments showed that a non-coding RNA sequence called CUT60, appeared to be important to help yeast cells grow. When CUT60 was modified so that it lacked the end marker, its RNA transcript fused with the neighbouring gene called ATP16. As a result, the protein of the ATP16 gene could no longer be produced properly. Normally, ATP16 plays important roles in a cell structure called the mitochondrion, also known as the energy powerhouse of the cell. The mitochondrion has its own DNA, and without CUT60 and ATP16, the yeast cells lost their mitochondrial DNA and could not grow as quickly.
This shows that non-coding DNA sequences can have a purpose and can affect other parts of the cell. Moreover, start and end markers of transcription are also important in non-coding DNA sequences. The same mechanism could be at play in other genes or even other organisms. As well as revealing a new role for non-coding DNA, the findings could also help to develop a new method to cleanse yeast cells of disease-causing mutations in their mitochondrial DNA.
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