游离的HIV-1 TAR RNA中存在碱基三联体的证据。
Evidence for a base triple in the free HIV-1 TAR RNA.
作者信息
Huthoff Hendrik, Girard Frederic, Wijmenga Sybren S, Berkhout Ben
机构信息
Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
出版信息
RNA. 2004 Mar;10(3):412-23. doi: 10.1261/rna.5161304.
We propose the existence of a novel base triple in the HIV-1 TAR hairpin. This triple is supported by covariation of loop residue 31 with residue 22, which is part of an unusual base pair with U40 below the 3-nucleotide bulge. A set of mutants was constructed to test the involvement of bases A22, U31, and U40 in a triple interaction. RNA structure probing, trans-activation assays, and structure modeling are consistent with the existence of this base triple in a bent conformation of the free TAR element. However, disruption of the base triple does not affect binding of a Tat-derived peptide. We therefore compared the structure of free and Tat-bound TAR RNA by footprinting and site-specific cross-linking analyses. These studies indicate that the Tat arginine-rich motif, in addition to its known binding site at the bulge, is in close contact with U31 in the TAR loop. Because binding of Tat to TAR is known to coincide with the formation of a base triple with residues U23, A27, and U38, we hypothesize that Tat binding and the associated straightening of TAR triggers the disruption of the (A22-U40)U31 triple.
我们提出在HIV-1 TAR发夹结构中存在一种新型碱基三联体。这种三联体由环残基31与残基22的共变所支持，残基22是在3核苷酸凸起下方与U40形成异常碱基对的一部分。构建了一组突变体以测试碱基A22、U31和U40在三联体相互作用中的作用。RNA结构探测、反式激活测定和结构建模与这种碱基三联体在游离TAR元件的弯曲构象中的存在一致。然而，碱基三联体的破坏并不影响Tat衍生肽的结合。因此，我们通过足迹分析和位点特异性交联分析比较了游离的和与Tat结合的TAR RNA的结构。这些研究表明，Tat富含精氨酸的基序，除了其在凸起处已知的结合位点外，还与TAR环中的U31紧密接触。因为已知Tat与TAR的结合与与残基U23、A27和U38形成碱基三联体重合，我们推测Tat结合以及相关的TAR拉直会触发(A22-U40)U31三联体的破坏。
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