3-ethyl C (3etC)

FULL NAME: 3-ethylcytosine


DESCRIPTION:
N3-ethylcytosine (3EtC), is formed by ethylating agents in single-stranded DNA and also has been detected in vitro and in vivo. As with the 1-alkyladenines, these lesions probably exist only or predominantly in single-stranded DNA because this site of modification is normally protected by base pairing. In E.coli, the AlkB protein has good activity against 3MeC and 3EtC both in vitro and in vivo. The appreciable mutagenesis and toxicity of the 3-alkylcytosines in vivo is decimated by AlkB, although a portion of the toxicity can also be overcome by induction of the SOS bypass polymerases. With regard to mutagenic potential, if a cell has no AlkB and uninduced SOS bypass polymerases, 3MeC and 3EtC are 30% mutagenic, with the predominant mutations being C → T and C → A. Basal expression of AlkB of a few molecules per cell abrogates the mutagenicity of 3MeC and 3EtC, whereas expression of SOS bypass polymerases in the absence of AlkB increases the mutagenicity of both lesions to a striking 70%.

DAMAGE TYPE: alkylation damage


DNA DAMAGE SOURCE(S) (MAIN):
ethyl methanesulfonate (EMS)
N-ethyl-N-nitrosourea (ENU)
alkylating agents


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


DNA DAMAGE EFFECT(S) (MINOR):
C→A transversion
mutagenesis
point mutation
substitution
transversion


PATHWAYS:
direct reversal (DR)


DNA repair protein(s) related to damage:
AlkB


Last modification date: Oct. 17, 2011