Structure of a DNA analog of the primer for HIV-1 RT second strand synthesis.
The non-self-complementary DNA decamer C-A-A-A-G-A-A-A-A-G/C-T-T-T-T-C-T-T-T-G is a DNA/DNA analogue of a portion of the polypurine tract or PPT, which is a RNA/DNA hybrid that serves as a primer for synthesis of the (+) DNA strand by HIV reverse transcriptase (RT), and which is not digested by the RNase H domain of reverse transcriptase following (-) strand synthesis. The same unusual conformation that eludes RNase H, thought to be a change in width of minor groove, may also be responsible for the inhibition of HIV RT by minor groove binding drugs such as distamycin and their bis-linked derivatives. The present X-ray crystal structure of this DNA decamer exhibits the usual properties of A-tract B-DNA under biologically relevant conditions: large propeller twist of base-pairs, narrowed minor groove, and a straight helix axis. Groove narrowing is fully developed in the A-A-A-A region, but not in the A-A-A region, which previous investigators have proposed as being too short to exhibit typical A-tract properties. The RNA/DNA hybrid produced by HIV reverse transcriptase during (-) strand synthesis presumably forms a "heteromerous" or H-helix with narrower minor groove than an A-helical RNA/RNA duplex. If the narrowing of minor groove in A-tract H-helices is comparable to that seen in A-tract B-helices, then the narrowed minor groove of the polypurine tract could make the second primer site both (1) impervious to RNase H digestion, and (2) susceptible to inhibition by minor groove binding drugs.
Han
G W
GW
Molecular Biology Institute, University of California at Los Angeles, 90095, USA.
Kopka
M L
ML
Cascio
D
D
Grzeskowiak
K
K
Dickerson
R E
RE
D018360:Crystallography, X-Ray; D017931:DNA Primers / Q000737:chemistry*; D004279:DNA, Viral / Q000737:chemistry*; D054303:HIV Reverse Transcriptase / Q000378:metabolism; D015497:HIV-1 / Q000201:enzymology; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry; D012367:RNA, Viral / Q000737:chemistry; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry*
D017931:DNA Primers; D004279:DNA, Viral; D009692:Nucleic Acid Heteroduplexes; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D054303:HIV Reverse Transcriptase