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Protein hnRNP A1 and its derivative Up1 unfold quadruplex DNA in the human KRAS promoter: implications for transcription.

ABSTRACT: The promoter of the human KRAS proto-oncogene contains a structurally polymorphic nuclease hypersensitive element (NHE) whose purine strand forms a parallel G-quadruplex structure (called 32R). In a previous work we reported that quadruplex 32R is recognized by three nuclear proteins: PARP-1, Ku70 and hnRNP A1. In this study we describe the interaction of recombinant hnRNP A1 (A1) and its derivative Up1 with the KRAS G-quadruplex. Mobility-shift experiments show that A1/Up1 binds specifically, and also with a high affinity, to quadruplex 32R, while CD demonstrates that the proteins strongly reduce the intensity of the 260 nm-ellipticity-the hallmark for parallel G4-DNA-and unfold the G-quadruplex. Fluorescence resonance energy transfer melting experiments reveal that A1/Up1 completely abrogates the cooperative quadruplex-to-ssDNA transition that characterizes the KRAS quadruplex and facilitates the association between quadruplex 32R and its complementary polypyrimidine strand. When quadruplex 32R is stabilized by TMPyP4, A1/Up1 brings about only a partial destabilization of the G4-DNA structure. The possible role played by hnRNP A1 in the mechanism of KRAS transcription is discussed.

PROVIDER: S-EPMC2685089 | BioStudies | 2009-01-01T00:00:00Z

REPOSITORIES: biostudies

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hnRNPA1/UP1 Unfolds KRAS G-Quadruplexes and Feeds a Regulatory Axis Controlling Gene Expression.

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RGG-box in hnRNPA1 specifically recognizes the telomere G-quadruplex DNA and enhances the G-quadruplex unfolding ability of UP1 domain.

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Role of Poly [ADP-ribose] Polymerase 1 in Activating the Kirsten ras (KRAS) Gene in Response to Oxidative Stress.

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