Introduction: Increased excision of
NRTIs is imparted by Excision Enhancement Mutations, typically
M41L,
D67N,
K70R,
T215Y/F,
L210W, and
K219E/Q (also known as Thymidine Associated Mutations, or TAMs).
Discussion: Mutations at position 70 of
RT have been known to confer
NRTI resistance by two distinct mechanisms:
K70R combined with at least two excision enhancing mutations,
D67N and
T215Y, enhances ATP-mediated excision of AZT and d4T (excision-dependent mechanism).