Table 1.

Major DNA Repair Processes and Projected Involvement in 5-FU Response.

DNA Repair Pathway	Primary DNA Substrates	Anticipated Involvement
MGMT = O6-methylguanine DNA methyltransferase
ABH = AlkB homolog dioxygenase
Direct Reversal		None
MGMT	O6-alkylguanine
ABH family	N1-alkylpurines
	N3-alkylpyrimidines
BER	Small base modifications, abasic sites, SSBs	See Section 3
MMR	Base-base mismatches and small insertion/deletion loops	See Section 4.1
NER	Helix-distorting base adducts	untested, unlikely
Recombination
NHEJ	DSBs	Not likely
HR	DSBs and collapsed replication forks	See Section 4.2