Melanoma Differentiation-Associated gene 5 (MDA5), encoded by the gene IFIH1, is a cytoplasmic sensor for viral double-stranded RNAs (dsRNAs). MDA5 activates the type I interferon signaling pathway upon detection of long viral dsRNA generated during replication of picornaviruses. Studies have shown that MDA5 forms a filament along the length of dsRNA and utilizes ATP-dependent filament dynamics...

We have re-examined the Ca(++)-dependent interaction of an intestinal microvillar 95- kdalton protein (MV-95K) and actin using the isolated acrosomal process bundles from limulus sperm. Making use of the processes as nuclei for assembling actin filaments, we quantitatively and qualitatively examined MV-95K's effect on filament assembly and on F- actin, both in the presence and in the absence of...

The thick-filament-monomeric-myosin equilibrium was prepared from pure myosin at pH 8.1. The application of hydrostatic pressure to the self-assembly equilibrium resulted in a biphasic dissociation curve in which a linear decrease in turbidity (a measure of weight added to or lost from the filament) was followed by a transition to a second pressure-insensitive phase. The first phase represents ...

Force production in skeletal muscle is proportional to the amount of overlap between the thin and thick filaments, which, in turn, depends on their lengths. Both thin- and thick-filament lengths are precisely regulated and uniform within a myofibril. While thick-filament lengths are essentially constant across muscles and species (∼1.65 μm), thin-filament lengths are highly variable both across...

At the leading edge of healing embryonic epithelium, cables of actin filaments appear to extend from cell to cell, forming a ring around the wound circumference. It has been hypothesized that this actin filament cable functions as a contractile 'purse string' to facilitate wound closure. We have observed this cable in large, circular healing epithelial wounds in corneas of adult mice. To elucid...

When a liquid drop falls from a fluid source with a slow flow rate, it remains attached to the source by an elongating liquid filament until the filament pinches off. For many fluids, this pinch-off occurs first near the end of the filament, where the filament joins to the liquid drop. For other fluids, the filament pinches off at one or more interior points. In this paper, we study the motion ...

Rad51 and Rad54 proteins are important for the repair of double-stranded DNA (dsDNA) breaks by homologous recombination in eukaryotes. Rad51 assembles on single-stranded DNA (ssDNA) to form a helical nucleoprotein filament that performs homologous pairing with dsDNA; Rad54 stimulates this pairing substantially. Here, we demonstrate that Rad54 acts in concert with the mature Rad51-ssDNA filament...

RecA and its homologs help maintain genomic integrity through recombination. Using single-molecule fluorescence assays and hidden Markov modeling, we show the most direct evidence that a RecA filament grows and shrinks primarily one monomer at a time and only at the extremities. Both ends grow and shrink, contrary to expectation, but a higher binding rate at one end is responsible for direction...

RecA proteins form a long stable filament on a single-stranded DNA and catalyze strand exchange reaction. The stability of RecA filament changes dramatically with pH, yet its detailed mechanism is not known. Here, using a single molecule assay, we determined the binding and dissociation rates of RecA monomers at the filament ends at various pH. The pH-induced rate changes were moderate but occu...

This paper presents one efficient automatic detection method for filament disappearance. The method was applied to the Big Bear Solar Observatory (BBSO) fulldisk Hα images. The initial step is to detect the filament pixels by the threshold method. Then, using a regiongrowing method, we merge the adjacent detected pixels to obtain all filament areas. Based on these two steps, an automatic filame...