Protein hnRNP A1 and its derivative Up1 unfold quadruplex DNA in the human KRAS promoter: implications for transcription.
Nucleic Acids Res
; 37(9): 2841-53, 2009 May.
Article
de En
| MEDLINE
| ID: mdl-19282454
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.
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Protéines proto-oncogènes
/
Régions promotrices (génétique)
/
Protéines G ras
/
Ribonucléoprotéine nucléaire hétérogène du groupe A-B
/
G-quadruplexes
Limites:
Humans
Langue:
En
Journal:
Nucleic Acids Res
Année:
2009
Type de document:
Article
Pays d'affiliation:
Italie