{Reference Type}: Journal Article
{Title}: The mechanism of UP1 binding and unfolding of human telomeric DNA G-quadruplex.
{Author}: Ling X;Yao Y;Ding L;Ma J;
{Journal}: Biochim Biophys Acta Gene Regul Mech
{Volume}: 1866
{Issue}: 4
{Year}: 2023 12 16
{Factor}: 6.304
{DOI}: 10.1016/j.bbagrm.2023.194985
{Abstract}: The human telomere contains multiple copies of the DNA sequence d(TTAGGG) which can fold into higher order intramolecular G-quadruplexes and regulate the maintenance of telomere length and chromosomal integrity. The nucleic acid binding protein heteronuclear ribonucleoprotein A1 (hnRNP A1) and its N-terminus proteolytic product UP1 have been shown to efficiently bind and unfold telomeric DNA G-quadruplex. However, the understanding of the molecular mechanism of the UP1 binding and unfolding telomeric G-quadruplexes is still limited. Here, we performed biochemical and biophysical characterizations of UP1 binding and unfolding of human telomeric DNA G-quadruplex d[AGGG(TTAGGG)3], and in combination of systematic site-direct mutagenesis of two tandem RNA recognition motifs (RRMs) in UP1, revealed that RRM1 is responsible for initial binding and unfolding, whereas RRM2 assists RRM1 to complete the unfolding of G-quadruplex. Isothermal titration calorimetry (ITC) and circular dichroism (CD) studies of the interactions between UP1 and DNA G-quadruplex variants indicate that the "TAG" binding motif in Loop2 of telomeric G-quadruplex is critical for UP1 recognition and G-quadruplex unfolding initiation. Together we depict a model for molecular mechanism of hnRNP A1 (UP1) binding and unfolding of the human telomeric DNA G-quadruplex.