![]() Only a handful of proteins have been shown to have the ability to rewind DNA, including RecG and UvsW ( 18). Some proteins within the family act as ATP-dependent DNA translocases, while others have been shown to generate torsion within DNA ( 17) or to affect other DNA–protein interactions ( 14). The Snf2 family consists of ATP-hydrolyzing proteins and they have been identified in eukaryotes, eubacteria, and archea ( 14, 15). Despite the presence of these helicase motifs, no Snf2 protein has been shown to exhibit helicase-like activity ( 15, 16). Furthermore, with its helicase-like region similar to the primary sequence of Saccharomyces cerevisiae Snf2p, it belongs to the Snf2 family ( 14, 15). HARP is a member of the helicase superfamily 2 (SF2) due to the amino acid-sequence similarity of seven helicase motifs ( 14). It has been shown that HARP is recruited to sites of DNA damage in vivo ( 10) by RPA, and it is thought that HARP has a role in replication fork restart and repair ( 11– 13). It has been termed an annealing helicase because it has the reverse action of helicases that more commonly unwind DNA and allow single-stranded binding protein to bind ssDNA. ![]() Hep-A related protein, HARP, also known as SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1), has the uncommon ability to re-anneal RPA-stabilized DNA bubbles into double-stranded DNA ( 9) via adenosine triphosphate (ATP) hydrolysis. It is heavily involved in replication, repair and recombination to protect and stabilize DNA. RPA, the most abundant single-stranded-binding protein in mammalian cells ( 6), consists of three subunits ( 7) and four binding domains that enable an unstable 8 nt, and a stable 30 nt binding mode ( 8). These can be stabilized by the single-stranded-binding proteins such as replication protein A (RPA) which subsequently may affect DNA processing ( 5). Under physiological values of applied force and torque, these negatively supercoiled DNA domains have a propensity to spontaneously form bubbles ( 4). Unwinding of dsDNA is ubiquitous in the cell, occurring during transcription, replication and repair ( 1), leading to a prevalence of negative supercoiling of DNA in cells ( 2, 3). Our work also allows the determination of some important features of RPA-bubble structures at low supercoiling, including the existence of multiple bubbles and that RPA molecules are mis-registered on the two strands. The enzyme exhibits classical Michaelis–Menten kinetics and acts cooperatively with a Hill coefficient of 3 ± 1. The dependence of the closing rate on both ionic strength and HARP concentration indicates that removal of RPA occurs via an association-dissociation mechanism where HARP does not remain associated with the DNA. The data indicate that DNA re-anneals through the removal of RPA, which is observed as clear steps in the bubble-closing traces. We find that HARP closes RPA-stabilized bubbles in a slow reaction, taking on the order of tens of minutes for ∼600 bp of DNA to be re-annealed. Using a single-molecule magnetic tweezers assay, we construct RPA-stabilized DNA bubbles within torsionally constrained DNA to investigate the annealing action of HARP on a physiologically relevant substrate. bhp files created with this app will load on both Mac and iOS versions.We investigate the mechanistic nature of the Snf2 family protein HARP, mutations of which are responsible for Schimke immuno-osseous dysplasia. ![]() Rated #1 Music App and Apple's Top Music App in many countries, since its release. Now it’s available as a Mac application that also makes music. Bubble Harp was first released as a work of interactive art by Scott Sona Snibbe that was only available in galleries and museums. Through the pop-up control panel at the screen’s bottom, you can change from single points to streams of points, change graphic and sonic parameters, and load and save files. You can record long movements of a single point, or stream many points out of your cursor like ink. It’s a combination of drawing, animation, music, art, geometry, and gaming. ![]() ** #1 Music App in Mac App Store Worldwide ** iTunes Top 10 App of the Year for Art and Music on iOS **īubble Harp draws bubbles around your mouse’s strokes, recording and replaying your movements while creating music. "Of the millions of apps out there, none quite capitalize on the sheer fun and beauty of interactivity the way that Scott Snibbe’s do.” -CoolHunting or Android KitKat 4.4, Lollipop 5.0, Marshmallow 6.0, Nougat 7.0, Oreo 8.0, Android Pie 9.0, Quince Tart 10, Red velvet cake 11, Snow cone 12 or later versions
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