Important DNA Repair Mechanism Linked To Premature Aging Yields
Important DNA Repair Mechanism Linked To Premature Aging Yields: "Genes are copied into messenger RNA by the large, complex molecular machine known as RNA polymerase II (RNAPII). RNAPII works by separating the two strands of the DNA helix � opening what's called a 'transcription bubble' � and moving along the strand to be transcribed like an engine along a cog railway, copying the genetic information in the gene to create a length of messenger RNA as it goes.
As the RNAPII engine trundles along, enclosing the DNA and the open bubble, it sometimes encounters a damaged nucleotide on the strand it is transcribing � the sort of damage that might have been inflicted by ultraviolet radiation or oxidative damage, for example. Or it may encounter situations such as a highly repetitive sequence of bases, with folding of the DNA upon itself, which make progress difficult. Unable to continue copying, RNAPII pauses and sometimes grinds to a halt.
Exposure to sunlight causes decreased transcription when ultraviolet-induced DNA damage blocks RNAPII. Transcription-coupled repair normally removes the blocking damage and allows transcription to recover; in Cockayne Syndrome, however, transcription cannot resume, and the affected cells die."
As the RNAPII engine trundles along, enclosing the DNA and the open bubble, it sometimes encounters a damaged nucleotide on the strand it is transcribing � the sort of damage that might have been inflicted by ultraviolet radiation or oxidative damage, for example. Or it may encounter situations such as a highly repetitive sequence of bases, with folding of the DNA upon itself, which make progress difficult. Unable to continue copying, RNAPII pauses and sometimes grinds to a halt.
Exposure to sunlight causes decreased transcription when ultraviolet-induced DNA damage blocks RNAPII. Transcription-coupled repair normally removes the blocking damage and allows transcription to recover; in Cockayne Syndrome, however, transcription cannot resume, and the affected cells die."