Sunday, June 14, 2009

New DNA Damage Repair Mechanism Must Have Arisen Early

DNA damage repair is a fascinating topic in cell biology. Fascinating because the cell's repair mechanisms are so incredible. What's more the mechanisms are coordinated in a sophisticated control network. As one researcher put it, "it’s almost as if cells have something akin to a computer program that becomes activated by DNA damage, and that program enables the cells to respond very quickly."

Now a new mechanism has been discovered which repairs DNA alkylation damage (the erroneous addition of carbon groups to DNA bases). The new mechanism links two previously known mechanisms. Here is how one science writer describes these two mechanisms:

The DNA repair process that removes such toxic "lesions" is known as base repair, and uses a protein called AGT (O6-alkylguanine DNA-alkytransferase) to remove the alkyl group before DNA replicates. The protein essentially sticks a chemical finger inside the DNA to flip the damaged [base] out from the DNA helix structure so that its adduct is exposed and can be transferred from the [base] to a part of its protein structure. The [base] is now repaired and can rejoin cytosine with three hydrogen bonds linking them.

AGT is believed to act alone, but there is another, unrelated repair process—nucleotide excision repair (NER)—that uses lots of proteins in its pathway. This repair occurs when bulky adducts stuck to bases distort the sleek shape of the DNA helix. Then a whole group of proteins come in and remove a patch of bases that includes the adduct, and DNA polymerase follows and fills in the patch while adding the correct base back.

The new mechanism uses alkyltransferase-like proteins (ATLs) which are similar to the AGT protein. Like AGT, ATL attacks the DNA base that has suffered alkylation damage. But the ATL protein distorts the DNA structure significantly, and thus triggers the NER mechanism.

This sophisticated and coordinated repair sequence was found in all three domains of life (prokaryotes, eukaryotes and archaea). For evolutionists this forces the absurd conclusion that such a sophisticated DNA repair interaction evolved early on. Before there was so much as an amoeba evolution had worked wonders. The earliest crude cells must not have been so crude after all. Evolution incredibly worked miracles when life first arose. As the researchers write:

Our analysis of lesion-binding site conservation identifies new ATLs in sea anemone and ancestral archaea, indicating that ATL interactions are ancestral to present-day repair pathways in all domains of life.

This conclusion that complexity comes early is often forced on evolutionists, in spite of the evolutionary expectations to the contrary.