In HIV-1, development of resistance to AZT (3′-azido-3′-deoxythymidine) is mediated by the acquisition of thymidine analogue resistance mutations (TAMs) (i.e., M41L, D67N, K70R, L210W, T215F/Y, and K219E/Q) in the viral reverse transcriptase (RT). Clinically relevant combinations of TAMs, such as M41L/T215Y or D67N/K70R/T215F/K219Q, enhance the ATP-mediated excision of AZT monophosphate (AZTMP) from the 3′ end of the primer, allowing DNA synthesis to continue. Additionally, during HIV-1 maturation, the Gag polyprotein is cleaved to release a mature nucleocapsid protein (NCp7) and two intermediate precursors (NCp9 and NCp15). NC proteins interact with the viral genome and facilitate the reverse transcription process. Using wild-type and TAM-containing RTs, we showed that both NCp9 and NCp15 inhibited ATP-mediated rescue of AZTMP-terminated primers annealed to RNA templates but not DNA templates, while NCp7 had no effect on rescue activity. RNase H inactivation by introducing the active-site mutation E478Q led to the loss of the inhibitory effect shown by NCp9. NCp15 had a stimulatory effect on the RT’s RNase H activity not observed with NCp7 and NCp9. However, analysis of RNase H cleavage patterns revealed that in the presence of NCp9, RNA/DNA complexes containing duplexes of 12 bp had reduced stability in comparison with those obtained in the absence of NC or with NCp7 or NCp15. These effects are expected to have a strong influence on the inhibitory action of NCp9 and NCp15 by affecting the efficiency of RNA-dependent DNA polymerization after unblocking DNA primers terminated with AZTMP and other nucleotide analogues.

中文翻译：

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核仁蛋白前体NCp9和NCp15通过HIV-1逆转录酶抑制ATP介导的AZT终止引物的救援。

在HIV-1中，对AZT（3'-叠氮基3'-脱氧胸苷）的耐药性的发展是通过获得胸苷类似物耐药性突变（TAM）（例如M41L，D67N，K70R，L210W，T215F / Y和病毒逆转录酶（RT）中的K219E / Q）。TAM的临床相关组合，例如M41L / T215Y或D67N / K70R / T215F / K219Q，可增强ATP介导的从引物3'端切除AZT单磷酸酯（AZTMP）的能力，从而使DNA合成得以继续。此外，在HIV-1成熟期间，Gag多蛋白被裂解以释放成熟的核衣壳蛋白（NCp7）和两个中间前体（NCp9和NCp15）。NC蛋白与病毒基因组相互作用并促进逆转录过程。使用野生型和含TAM的RT，我们发现NCp9和NCp15都抑制了ATP介导的AZTMP终止引物退火，该引物与RNA模板退火，而与DNA模板退火，而NCp7对救援活性没有影响。通过引入活性位点突变E478Q使RNase H失活导致NCp9所示的抑制作用丧失。NCp15对RT的RNase H活性具有刺激作用，而NCp7和NCp9则未观察到。但是，对RNase H裂解模式的分析表明，与不存在NC或NCp7或NCp15时相比，存在NCp9时，包含12 bp双链体的RNA / DNA复合物的稳定性降低。