thymine glycol (Tg)

FULL NAME: 5,6-dihydroxy-5,6-dihydrothymidine


DESCRIPTION:
Thymine glycol (5,6-dihydro-5,6-dihydroxythymine) is one of the principal DNA lesions induced by oxidation, ionizing radiation, and other oxidative mutagens. Thymine glycol is a major type of oxidative DNA damage that results from the reaction of a thymine base with reactive oxygen species generated by ionizing radiation or as a consequence of aerobic metabolism. While this damage causes mutations only at a low frequency, it effectively blocks DNA replication and must be repaired by the base excision repair pathway. Thymine glycol leads to mutagenesis T-->C and C→T transitions. Oxygen radicals react with 5-methylcytosine to oxidize the 5,6‐double bond; the intermediate product, 5-methylcytosine glycol, then deaminates to form thymine glycol. Thymine glycol base pairs with A and results in a C→T transition. It is a weak mutagen and it blocks transcription and replication. This lesion is primarily repaired by the BER pathway.

DAMAGE TYPE: hydrate


DNA DAMAGE SOURCE(S) (MAIN):
reactive oxygen species (ROS)
ionizing radiation (IR)
UV radiation


DNA DAMAGE EFFECT(S) (MAIN):
C→T transition
mutagenesis
point mutation
stalled replication fork
substitution
T→C transition
transition


PATHWAYS:
base excision repair (BER)


DNA repair protein(s) related to damage:
Fpg (MutM)
Nei (endo VIII)
NEIL2
NTHL1
Nth (endo III)


Last modification date: Oct. 9, 2011