Molecular "Clocks" Control Mutation Rate in Human Cells

DNA is contained within every cell of the human body, throughout the life time the cells become exposed to internal and external mutational factors causing mutations in the DNA.  These processes affect the body in different patterns; external exposures often affect the DNA in a burst pattern, other internal processes of the cell cause mutations at a constant rate over the lifetime.  Some of these mutations generated by these internal processes will be "clock like" with the number of mutations present at a current age.   

Research recently published in the journal of Nature Genetics identified two clock-like mutational processes and the rate at which the two clocks tick in different human cells.  Dr Ludmil Alexandrov, Oppenheimer Fellow at Los Alamos National Laboratory in the USA, and a team of researchers examined the DNA sequences of 10,250 cancer genomes from 36 different types of cancer to identify mutational signatures of mutational clocks.  The research team focused on the DNA of cancer cells because there is a fingerprint that is left behind when a mutation occurs in a cell, this fingerprint is referred as a mutation signature.  Results from the research produced 33 mutational signatures in a cancer genome, of those 33, two had clock like features; termed signature 1 and signature 5.  Both signatures showed a correlation between the number of mutations found in a cancer cell and the age of the patient when diagnosed with cancer.  Both signature 1 and signature 5 clock-like processes accumulated mutations at a constant rate over time and operate in essentially all cell types in the human body.  

This research is important in understanding the rates at which mutations occur in cells and possibly the rate at which cancer spreads throughout the body.  The rate of these mutational signatures can be an indication of aging patterns and the likelihood of certain cells to become cancerous.